Editing Germanium

{{short description|Chemical element with atomic number 32}}
{{distinguish|geranium}}
{{pp-move}}
{{infobox germanium}}
'''Germanium''' is a [[chemical element]]; it has [[Symbol (chemistry)|symbol]] '''Ge''' and [[atomic number]] 32. It is lustrous, hard-brittle, grayish-white and similar in appearance to [[silicon]]. It is a [[metalloid]] or a [[nonmetal]] in the [[carbon group]] that is chemically similar to [[silicon]]. Like silicon, germanium naturally [[Chemical reaction|reacts]] and forms complexes with [[oxygen]] in nature.

Because it seldom appears in high concentration, germanium was found comparatively late in the [[Timeline of chemical element discoveries|discovery of the elements]]. Germanium ranks 50th [[Abundance of elements in Earth's crust|in abundance of the elements in the Earth's crust]]. In 1869, [[Dmitri Mendeleev]] [[Mendeleev's predicted elements|predicted]] its existence and some of its [[Chemical property|properties]] from its position on his [[periodic table]], and called the element '''ekasilicon'''. On February 6, 1886, [[Clemens Winkler]] at Freiberg University found the new element, along with [[silver]] and [[sulfur]], in the mineral [[argyrodite]]. Winkler named the element after Germany, his country of birth. Germanium is mined primarily from [[sphalerite]] (the primary ore of [[zinc]]), though germanium is also recovered commercially from silver, [[lead]], and [[copper]] ores.

Elemental germanium is used as a semiconductor in [[transistor]]s and various other electronic devices. Historically, the first decade of semiconductor electronics was based entirely on germanium. Presently, the major end uses are [[fibre-optic]] systems, [[Night-vision device|infrared optics]], [[solar cell]] applications, and [[light-emitting diode]]s (LEDs). Germanium compounds are also used for [[polymerization]] catalysts and have most recently found use in the production of [[nanowire]]s. This element forms a large number of [[organogermanium compound]]s, such as [[tetraethylgermanium]], useful in [[organometallic chemistry]].

Germanium is not thought to be an essential element for any [[Organic chemistry|living organism]]. Similar to silicon and aluminium, naturally-occurring germanium compounds tend to be insoluble in water and thus have little oral [[toxicity]]. However, synthetic soluble germanium salts are [[nephrotoxic]], and synthetic chemically reactive germanium compounds with [[halogen]]s and [[hydrogen]] are irritants and toxins.

== History ==
<!--[[File:medeleeff by repin.jpg|thumb|Dmitri Mendeleev|alt=An old man with a gray-white beard sitting by the table, holding an old open book in his laps. He wears a red-blue gown and black square hat. There are two thick old books on the table.]]
[[File:Winkler Clemens.jpg|thumb|[[Clemens Winkler]]|alt=Photo of a bust of a middle-aged man in a suit with a white short beard and gray moustache.]] THESE PHOTOS are hard to arrange due to the infobox; they are not essential for Germanium-->
[[File:Mendeleev 1869 prediction of germanium (detail).svg|upright|left|thumb |Prediction of germanium, "?=70" (periodic table 1869)]]
In his report on ''The Periodic Law of the Chemical Elements'' in 1869, the Russian chemist [[Dmitri Mendeleev]] predicted the existence of several unknown chemical elements, including one that would fill a gap in the [[group 14 element|carbon family]], located between [[silicon]] and [[tin]].<ref>{{cite journal |first=Masanori |last=Kaji |title=D. I. Mendeleev's concept of chemical elements and ''The Principles of Chemistry'' |journal=Bulletin for the History of Chemistry |volume=27 |issue=1 |pages=4–16 |year=2002 |doi=10.70359/bhc2002v027p004 |url=http://www.scs.uiuc.edu/~mainzv/HIST/awards/OPA%20Papers/2005-Kaji.pdf |access-date=2008-08-20 |archive-url=https://web.archive.org/web/20081217080509/http://www.scs.uiuc.edu/~mainzv/HIST/awards/OPA%20Papers/2005-Kaji.pdf |archive-date=2008-12-17 |url-status=dead}}</ref> Because of its position in his periodic table, Mendeleev called it ''ekasilicon (Es)'', and he estimated its [[atomic weight]] to be 70 (later 72).<!-- Mendeleev studied several minerals in an unsuccessful search for this new element.<ref name="vdk">{{cite web |title=Elementymology & Elements Multidict: Germanium |first=Peter |last=van der Krogt |url=http://elements.vanderkrogt.net/element.php?sym=Ge |access-date=2008-08-20}}</ref> -->

<!-- [[File:Winkler preparate 1886 1904.png|thumb|left|Samples of germanium compounds prepared by Freiberg University's [[Clemens Winkler]], discoverer of the element]] -->In mid-1885, at a mine near [[Freiberg, Saxony]], a new [[mineral]] was discovered and named ''[[argyrodite]]'' because of its high [[silver]] content.{{NoteTag|From Greek, ''argyrodite'' means ''silver-containing''.<ref>{{cite report |url=http://www.handbookofmineralogy.org/pdfs/argyrodite.pdf |publisher=Mineral Data Publishing |title=Argyrodite – {{chem|Ag|8|GeS|6}} |access-date=2008-09-01 |date= |archive-date=2016-03-03 |archive-url=https://web.archive.org/web/20160303221645/http://www.handbookofmineralogy.org/pdfs/argyrodite.pdf |url-status=live}}</ref>}} The chemist [[Clemens Winkler]] analyzed this new mineral, which proved to be a combination of silver, sulfur, and a new element. Winkler was able to isolate the new element in 1886 and found it similar to [[antimony]]. He initially considered the new element to be eka-antimony, but was soon convinced that it was instead eka-silicon.<ref name="Winkle2" /><ref name="isolation">{{cite journal |journal=Berichte der Deutschen Chemischen Gesellschaft |volume=19 |issue=1 |pages=210–211 |title=Germanium, Ge, a New Nonmetal Element |language=de |first=Clemens |last=Winkler |author-link=Clemens Winkler |year=1887 |doi=10.1002/cber.18860190156 |url=http://gallica.bnf.fr/ark%3A/12148/bpt6k90705g/f212.chemindefer |url-status=dead |archive-url=https://web.archive.org/web/20081207033757/http://dbhs.wvusd.k12.ca.us/webdocs/Chem-History/Disc-of-Germanium.html |archive-date=December 7, 2008}}</ref> Before Winkler published his results on the new element, he decided that he would name his element ''neptunium'', since the recent discovery of planet [[Neptune]] in 1846 had similarly been preceded by mathematical predictions of its existence.{{NoteTag|Just as the existence of the new element had been predicted, the existence of the planet [[Neptune]] had been predicted in about 1843 by the two mathematicians [[John Couch Adams]] and [[Urbain Le Verrier]], using the calculation methods of [[celestial mechanics]]. They did this in attempts to explain the fact that the planet [[Uranus]], upon very close observation, appeared to be being pulled slightly out of position in the sky.<ref>{{cite journal |first=J. C. |last=Adams |bibcode=1846MNRAS...7..149A |title=Explanation of the observed irregularities in the motion of Uranus, on the hypothesis of disturbance by a more distant planet |journal=[[Monthly Notices of the Royal Astronomical Society]] |volume=7 |issue=9 |pages=149–152 |date=November 13, 1846 |doi=10.1093/mnras/7.9.149 |url=https://zenodo.org/record/1431905 |access-date=August 25, 2019 |archive-date=May 2, 2019 |archive-url=https://web.archive.org/web/20190502014753/https://zenodo.org/record/1431905/files/article.pdf |url-status=live |doi-access=free}}</ref> [[James Challis]] started searching for it in July 1846, and he sighted this planet on September 23, 1846.<ref>{{cite journal |first=Rev. J. |last=Challis |bibcode=1846MNRAS...7..145C |title=Account of observations at the Cambridge observatory for detecting the planet exterior to Uranus |journal=Monthly Notices of the Royal Astronomical Society |volume=7 |issue=9 |pages=145–149 |date=November 13, 1846 |doi=10.1093/mnras/7.9.145 |url=https://zenodo.org/record/1431903 |access-date=August 25, 2019 |archive-date=May 4, 2019 |archive-url=https://web.archive.org/web/20190504065619/https://zenodo.org/record/1431903/files/article.pdf |url-status=live |doi-access=free}}</ref>}} However, the name "neptunium" had already been given to another proposed chemical element (though not the element that today bears the name [[neptunium]], which was discovered in 1940).{{NoteTag|R. Hermann published claims in 1877 of his discovery of a new element beneath [[tantalum]] in the periodic table, which he named ''neptunium'', after the Greek god of the oceans and seas.<ref>{{cite journal |title=Scientific Miscellany |journal=The Galaxy |volume=24 |issue=1 |date=July 1877 |page=131 |isbn=978-0-665-50166-1 |first=Robert |last=Sears |oclc=16890343}}</ref><ref>{{cite journal |title=Editor's Scientific Record |journal=Harper's New Monthly Magazine |volume=55 |issue=325 |date=June 1877 |pages=152–153 |url=http://cdl.library.cornell.edu/cgi-bin/moa/moa-cgi?notisid=ABK4014-0055-21 |access-date=2008-09-22 |archive-date=2012-05-26 |archive-url=https://archive.today/20120526215615/http://cdl.library.cornell.edu/cgi-bin/moa/moa-cgi?notisid=ABK4014-0055-21 |url-status=live}}</ref> However this [[metal]] was later recognized to be an [[alloy]] of the elements [[niobium]] and tantalum.<ref>{{cite web |title=Elementymology & Elements Multidict: Niobium |first=Peter |last=van der Krogt |url=http://elements.vanderkrogt.net/element.php?sym=Nb |access-date=2008-08-20 |archive-date=2010-01-23 |archive-url=https://web.archive.org/web/20100123002753/http://elements.vanderkrogt.net/element.php?sym=Nb |url-status=live}}</ref> The name "[[neptunium]]" was later given to the synthetic element one step past [[uranium]] in the Periodic Table, which was discovered by [[nuclear physics]] researchers in 1940.<ref>{{cite book |title=Nobel Lectures, Chemistry 1942–1962 |publisher=Elsevier |date=1964 |chapter=The Nobel Prize in Chemistry 1951: presentation speech |first=A. |last=Westgren |chapter-url=http://nobelprize.org/nobel_prizes/chemistry/laureates/1951/press.html |access-date=2008-09-18 |archive-date=2008-12-10 |archive-url=https://web.archive.org/web/20081210174205/http://nobelprize.org/nobel_prizes/chemistry/laureates/1951/press.html |url-status=live}}</ref>}} So instead, Winkler named the new element ''germanium'' (from the [[Latin]] word, ''[[Germania]]'', for Germany) in honor of his homeland.<ref name="isolation" /> Argyrodite proved empirically to be Ag<sub>8</sub>GeS<sub>6</sub>.
Because this new element showed some similarities with the elements [[arsenic]] and antimony, its proper place in the periodic table was under consideration, but its similarities with Dmitri Mendeleev's predicted element "ekasilicon" confirmed that place on the periodic table.<ref name="isolation" /><ref>{{cite journal |journal=The Manufacturer and Builder |url=http://cdl.library.cornell.edu/cgi-bin/moa/pageviewer?frames=1&coll=moa&view=50&root=%2Fmoa%2Fmanu%2Fmanu0018%2F&tif=00187.TIF |year=1887 |title=Germanium, a New Non-Metallic Element |page=181 |access-date=2008-08-20 |archive-date=2008-12-19 |archive-url=https://web.archive.org/web/20081219162737/http://cdl.library.cornell.edu/cgi-bin/moa/pageviewer?frames=1&coll=moa&view=50&root=%2Fmoa%2Fmanu%2Fmanu0018%2F&tif=00187.TIF |url-status=live}}</ref> With further material from 500&nbsp;kg of ore from the mines in Saxony, Winkler confirmed the chemical properties of the new element in 1887.<ref name="Winkle2">{{cite journal |first=Clemens |last=Winkler |author-link=Clemens Winkler |journal=J. Prak. Chemie |volume=36 |issue=1 |date=1887 |pages=177–209 |title=Mittheilungen über des Germanium. Zweite Abhandlung |doi=10.1002/prac.18870360119 |url=http://gallica.bnf.fr/ark:/12148/bpt6k90799n/f183.table |access-date=2008-08-20 |language=de |archive-date=2012-11-03 |archive-url=https://web.archive.org/web/20121103012004/http://gallica.bnf.fr/ark:/12148/bpt6k90799n/f183.table |url-status=live}}</ref><ref name="isolation" /><ref>{{cite journal |first=O. |last=Brunck |title=Obituary: Clemens Winkler |journal=Berichte der Deutschen Chemischen Gesellschaft |volume=39 |issue=4 |year=1886 |pages=4491–4548 |doi=10.1002/cber.190603904164 |url=https://zenodo.org/record/1426200 |language=de |access-date=2020-06-07 |archive-date=2020-08-01 |archive-url=https://web.archive.org/web/20200801004057/https://zenodo.org/record/1426200 |url-status=live}}</ref> He also determined an atomic weight of 72.32 by analyzing pure [[germanium tetrachloride]] ({{chem|GeCl|4}}), while [[Lecoq de Boisbaudran]] deduced 72.3 by a comparison of the lines in the spark [[spectrum]] of the element.<ref>{{cite journal |title=Sur le poids atomique du germanium |first=M. Lecoq |last=de Boisbaudran |journal=Comptes Rendus |year=1886 |volume=103 |page=452 |url=http://gallica.bnf.fr/ark:/12148/bpt6k3059r/f454.table |access-date=2008-08-20 |language=fr |archive-date=2013-06-20 |archive-url=https://web.archive.org/web/20130620032945/http://gallica.bnf.fr/ark:/12148/bpt6k3059r/f454.table |url-status=live}}</ref>

Winkler was able to prepare several new compounds of germanium, including [[Germanium fluoride|fluorides]], [[Germanium chloride|chlorides]], [[Germanium sulfide (disambiguation)|sulfides]]<!--intentional link to DAB page-->, [[Germanium dioxide|dioxide]], and [[tetraethylgermane]] (Ge(C<sub>2</sub>H<sub>5</sub>)<sub>4</sub>), the first organogermane.<ref name="Winkle2" /> The physical data from those compounds—which corresponded well with Mendeleev's predictions—made the discovery an important confirmation of Mendeleev's idea of element [[Periodic table|periodicity]]. Here is a comparison between the prediction and Winkler's data:<ref name="Winkle2" />

<div style="float: center; margin: 5px;">
{| class="wikitable"
|-
! Property !! Ekasilicon<br />{{nobold|Mendeleev<br />prediction (1871)}} !! Germanium<br />{{nobold|Winkler<br />discovery (1887)}}
|-
| atomic mass || 72.64 || 72.63
|-
| density (g/cm<sup>3</sup>) || 5.5 || 5.35
|-
| melting point (°C) || high || 947
|-
| color || gray || gray
|-
| oxide type || [[refractory]] dioxide || refractory dioxide
|-
| oxide density (g/cm<sup>3</sup>) || 4.7 || 4.7
|-
| oxide activity || feebly basic || feebly basic
|-
| chloride boiling point (°C) || under 100 || 86 (GeCl<sub>4</sub>)
|-
| chloride density (g/cm<sup>3</sup>) || 1.9 || 1.9
|}</div>

Until the late 1930s, germanium was thought to be a poorly conducting [[metal]].<ref name="DOE">{{cite journal |title=Germanium: From Its Discovery to SiGe Devices |author=Haller, E. E. |website=Department of Materials Science and Engineering, University of California, Berkeley, and Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley |url=http://www.osti.gov/bridge/servlets/purl/922705-bthJo6/922705.PDF |access-date=2008-08-22 |date=2006-06-14 |archive-date=2019-07-10 |archive-url=https://web.archive.org/web/20190710154435/http://www.osti.gov/bridge/servlets/purl/922705-bthJo6/922705.PDF |url-status=live}}</ref> Germanium did not become economically significant until after 1945 when its properties as an [[electronics|electronic]] semiconductor were recognized. During [[World War II]], small amounts of germanium were used in some special [[electronics|electronic devices]], mostly [[diode]]s.<ref>{{cite news |author=W. K. |url=http://select.nytimes.com/gst/abstract.html?res=F30715FE3F5B157A93C2A8178ED85F478585F9 |newspaper=The New York Times |title=Germanium for Electronic Devices |access-date=2008-08-22 |date=1953-05-10 |archive-date=2013-06-13 |archive-url=https://web.archive.org/web/20130613202934/http://select.nytimes.com/gst/abstract.html?res=F30715FE3F5B157A93C2A8178ED85F478585F9 |url-status=live}}</ref><ref>{{cite web |url=http://www.computerhistory.org/semiconductor/timeline/1941-semiconductor.html |title=1941 – Semiconductor diode rectifiers serve in WW II |publisher=Computer History Museum |access-date=2008-08-22 |archive-date=2008-09-24 |archive-url=https://web.archive.org/web/20080924135754/http://www.computerhistory.org/semiconductor/timeline/1941-semiconductor.html |url-status=live}}</ref> The first major use was the point-contact [[Schottky diode]]s for [[radar]] pulse detection during the War.<ref name="DOE" /> The first [[silicon–germanium]] alloys were obtained in 1955.<ref>{{cite web |url=http://www.sp.phy.cam.ac.uk/~SiGe/Silicon%20Germanium%20(SiGe)%20History.html |title=SiGe History |publisher=University of Cambridge |access-date=2008-08-22 |url-status=dead |archive-url=https://web.archive.org/web/20080805204801/http://www.sp.phy.cam.ac.uk/~SiGe/Silicon%20Germanium%20%28SiGe%29%20History.html |archive-date=2008-08-05}}</ref> Before 1945, only a few hundred kilograms of germanium were produced in smelters each year, but by the end of the 1950s, the annual worldwide production had reached {{convert|40|MT|ST|lk=on|abbr=off}}.<ref name="acs">{{cite news |url=http://pubs.acs.org/cen/80th/print/germanium.html |year=2003 |title=Germanium |first=Bethany |last=Halford |work=Chemical & Engineering News |publisher=American Chemical Society |access-date=2008-08-22 |archive-date=2008-05-13 |archive-url=https://web.archive.org/web/20080513180858/http://pubs.acs.org/cen/80th/print/germanium.html |url-status=live}}</ref>

The development of the germanium [[transistor]] in 1948<ref>{{cite journal |journal=Physical Review |volume=74 |issue=2 |pages=230–231 |title=The Transistor, A Semi-Conductor Triode |first=J. |last=Bardeen |author2=Brattain, W. H. |year=1948 |doi=10.1103/PhysRev.74.230 |bibcode=1948PhRv...74..230B |doi-access=free}}</ref> opened the door to countless applications of [[solid state (electronics)|solid state electronics]].<ref>{{cite web |title=Electronics History 4 – Transistors |url=http://www.greatachievements.org/?id=3967 |publisher=National Academy of Engineering |access-date=2008-08-22 |archive-date=2007-10-20 |archive-url=https://web.archive.org/web/20071020030644/http://www.greatachievements.org/?id=3967 |url-status=live}}</ref> From 1950 through the early 1970s, this area provided an increasing market for germanium, but then high-purity silicon began replacing germanium in transistors, diodes, and [[rectifier]]s.<ref name="usgs">{{cite journal |title=Germanium – Statistics and Information |author=U.S. Geological Survey |year=2008 |journal=U.S. Geological Survey, Mineral Commodity Summaries |url=http://minerals.usgs.gov/minerals/pubs/commodity/germanium/ |quote=Select 2008 |access-date=2008-08-28 |archive-date=2008-09-16 |archive-url=https://web.archive.org/web/20080916115005/http://minerals.usgs.gov/minerals/pubs/commodity/germanium/ |url-status=live}}</ref> For example, the company that became [[Fairchild Semiconductor]] was founded in 1957 with the express purpose of producing silicon transistors. Silicon has superior electrical properties, but it requires much greater purity that could not be commercially achieved in the early years of [[solid-state electronics|semiconductor electronics]].<ref>{{cite journal |journal=IEEE Transactions on Electron Devices |volume=ED-23 |issue=7 |date=July 1976 |title=Single Crystals of Germanium and Silicon-Basic to the Transistor and Integrated Circuit |first=Gordon K. |last=Teal |pages=621–639 |doi=10.1109/T-ED.1976.18464 |bibcode=1976ITED...23..621T |s2cid=11910543}}</ref>

Meanwhile, the demand for germanium for [[fiber optics|fiber optic]] communication networks, infrared [[night vision]] systems, and [[polymerization]] [[catalysts]] increased dramatically.<ref name="acs" /> These end uses represented 85% of worldwide germanium consumption in 2000.<ref name="usgs" /> The US government even designated germanium as a strategic and critical material, calling for a 146&nbsp;[[Short ton|ton]] (132&nbsp;[[tonne]]) supply in the national defense stockpile in 1987.<ref name="acs" />

Germanium differs from silicon in that the supply is limited by the availability of exploitable sources, while the supply of silicon is limited only by production capacity since silicon comes from ordinary sand and [[quartz]]. While silicon could be bought in 1998 for less than $10 per kg,<ref name="acs" /> the price of germanium was almost $800 per kg.<ref name="acs" />

== Characteristics ==

Under [[standard conditions]], germanium is a brittle, silvery-white,<ref name="nbb" /> [[semiconductor]]. This form constitutes an [[allotrope]] known as ''α-germanium'', which has a metallic luster and a [[diamond cubic|diamond cubic crystal structure]], the same structure as [[silicon]] and [[diamond]].<ref name="usgs" /> In this form, germanium has a [[threshold displacement energy]] of <math>19.7^{+0.6}_{-0.5}~\text{eV}</math>.<ref>{{Cite journal |last1=Agnese |first1=R. |last2=Aralis |first2=T. |last3=Aramaki |first3=T. |last4=Arnquist |first4=I. J. |last5=Azadbakht |first5=E. |last6=Baker |first6=W. |last7=Banik |first7=S. |last8=Barker |first8=D. |last9=Bauer |first9=D. A. |date=2018-08-27 |title=Energy loss due to defect formation from 206Pb recoils in SuperCDMS germanium detectors |journal=Applied Physics Letters |volume=113 |issue=9 |pages=092101 |doi=10.1063/1.5041457 |issn=0003-6951 |arxiv=1805.09942 |bibcode=2018ApPhL.113i2101A |s2cid=118627298}}</ref> At pressures above 120&nbsp;[[bar (unit)|kbar]], germanium becomes the metallic allotrope ''β-germanium'' with the same structure as β-[[tin]].<ref name="HollemanAF" /> Like silicon, [[gallium]], [[bismuth]], [[antimony]], and [[water]], germanium is one of the few substances that expands as it solidifies (i.e. [[freezing|freezes]]) from the molten state.<ref name="HollemanAF" />

Germanium is a semiconductor having an [[Direct and indirect band gaps|indirect bandgap]], as is crystalline silicon. [[Zone refining]] techniques have led to the production of crystalline germanium for semiconductors that has an impurity of only one part in 10<sup>10</sup>,<ref name="lanl">{{cite web |publisher=Los Alamos National Laboratory |title=Germanium |url=http://periodic.lanl.gov/32.shtml |access-date=2008-08-28 |archive-date=2011-06-22 |archive-url=https://web.archive.org/web/20110622065850/http://periodic.lanl.gov/32.shtml |url-status=live}}</ref>
making it one of the purest materials ever obtained.<ref>
{{cite book |title=The Primordial Universe: 28 June – 23 July 1999 |editor=Binetruy, B |chapter=Dark Matter: Direct Detection |author=Chardin, B. |publisher=Springer |date=2001 |isbn=978-3-540-41046-1 |page=308}}
</ref>
The first semi-metallic material discovered (in 2005) to become a [[superconductor]] in the presence of an extremely strong [[electromagnetic field]] was an [[Uranium rhodium germanium|alloy of germanium, uranium, and rhodium]].<ref>
{{cite journal |title=Magnetic field-induced superconductivity in the ferromagnet URhGe |last1=Lévy |first1=F. |last2=Sheikin |first2=I. |last3=Grenier |first3=B. |last4=Huxley |first4=A. |journal=Science |date=August 2005 |volume=309 |issue=5739 |pages=1343–1346 |pmid=16123293 |bibcode=2005Sci...309.1343L |doi=10.1126/science.1115498 |s2cid=38460998}}
</ref>

Pure germanium is known to spontaneously extrude very long [[screw dislocation]]s, referred to as ''germanium whiskers''. The growth of these whiskers is one of the primary reasons for the failure of older diodes and transistors made from germanium, as, depending on what they eventually touch, they may lead to an [[electrical short]].<ref>{{cite journal |title=Morphology of Germanium Whiskers |first=E. I. |last=Givargizov |journal=Kristall und Technik |volume=7 |issue=1–3 |doi=10.1002/crat.19720070107 |pages=37–41 |year=1972|bibcode=1972CryRT...7...37G }}</ref>

=== Chemistry ===
{{Main|Germanium compounds}}

Elemental germanium starts to oxidize slowly in air at around 250&nbsp;°C, forming [[germanium dioxide|GeO<sub>2</sub>]] .<ref>{{cite journal |doi=10.1016/S0169-4332(98)00251-7 |title=KRXPS study of the oxidation of Ge(001) surface |date=1998 |author=Tabet, N |journal=Applied Surface Science |volume=134 |issue=1–4 |pages=275–282 |bibcode=1998ApSS..134..275T |last2=Salim |first2=Mushtaq A.}}</ref> Germanium is insoluble in dilute [[acids]] and [[alkalis]] but dissolves slowly in hot concentrated sulfuric and nitric acids and reacts violently with molten alkalis to produce [[germanate]]s ({{chem|[GeO|3|]|2−}}). Germanium occurs mostly in the [[oxidation state]] +4 although many +2 compounds are known.<ref name = "Greenwood">{{Greenwood&Earnshaw}}</ref> Other oxidation states are rare: +3 is found in compounds such as Ge<sub>2</sub>Cl<sub>6</sub>, and +3 and +1 are found on the surface of oxides,<ref>{{cite journal |doi=10.1016/S0368-2048(98)00451-4 |title=XPS study of the growth kinetics of thin films obtained by thermal oxidation of germanium substrates |first3=A. L. |last3=Al-Oteibi |first2=M. A. |date=1999 |last2=Salim |author=Tabet, N |journal=Journal of Electron Spectroscopy and Related Phenomena |volume=101–103 |pages=233–238 |bibcode=1999JESRP.101..233T}}</ref> or negative oxidation states in [[germanide]]s, such as −4 in {{chem|Mg|2|Ge}}. Germanium cluster anions ([[Zintl phase|Zintl]] ions) such as Ge<sub>4</sub><sup>2−</sup>, Ge<sub>9</sub><sup>4−</sup>, Ge<sub>9</sub><sup>2−</sup>, [(Ge<sub>9</sub>)<sub>2</sub>]<sup>6−</sup> have been prepared by the extraction from alloys containing alkali metals and germanium in liquid ammonia in the presence of [[ethylenediamine]] or a [[cryptand]].<ref name = "Greenwood" /><ref>{{cite journal |title=Oxidative Coupling of Deltahedral [Ge<sub>9</sub>]<sup>4−</sup> Zintl Ions |first1=Li |last1=Xu |last2=Sevov |first2=Slavi C. |journal=J. Am. Chem. Soc. |date=1999 |volume=121 |issue=39 |pages=9245–9246 |doi=10.1021/ja992269s|bibcode=1999JAChS.121.9245X }}</ref> The oxidation states of the element in these ions are not integers—similar to the [[ozonide]]s O<sub>3</sub><sup>−</sup>.

Two [[oxide]]s of germanium are known: [[germanium dioxide]] ({{chem|GeO|2}}, germania) and [[germanium monoxide]], ({{chem|GeO}}).<ref name="HollemanAF">{{cite book |last=Holleman |first=A. F. |author2=Wiberg, E. |author3=Wiberg, N. |title=Lehrbuch der Anorganischen Chemie |edition=102nd |publisher=de Gruyter |date=2007 |isbn=978-3-11-017770-1 |oclc=145623740}}</ref> The dioxide, GeO<sub>2</sub>, can be obtained by roasting [[germanium disulfide]] ({{chem|GeS|2}}), and is a white powder that is only slightly soluble in water but reacts with alkalis to form [[germanate]]s.<ref name="HollemanAF" /> The monoxide, germanous oxide, can be obtained by the high temperature reaction of GeO<sub>2</sub> with elemental Ge.<ref name="HollemanAF" /> The dioxide (and the related oxides and germanates) exhibits the unusual property of having a high refractive index for visible light, but transparency to [[infrared]] light.<ref>{{cite journal |doi=10.1111/j.1151-2916.2002.tb00594.x |title=Infrared Transparent Germanate Glass-Ceramics |first=Shyam S. |last=Bayya |author2=Sanghera, Jasbinder S. |author3=Aggarwal, Ishwar D. |author4=Wojcik, Joshua A. |journal=Journal of the American Ceramic Society |volume=85 |issue=12 |pages=3114–3116 |date=2002}}</ref><ref>{{cite journal |doi=10.1007/BF00614256 |title=Infrared reflectance and transmission spectra of germanium dioxide and its hydrolysis products |date=1975 |last1=Drugoveiko |first1=O. P. |journal=Journal of Applied Spectroscopy |volume=22 |issue=2 |pages=191–193 |last2=Evstrop'ev |first2=K. K. |last3=Kondrat'eva |first3=B. S. |last4=Petrov |first4=Yu. A. |last5=Shevyakov |first5=A. M. |bibcode=1975JApSp..22..191D |s2cid=97581394}}</ref> [[Bismuth germanate]], Bi<sub>4</sub>Ge<sub>3</sub>O<sub>12</sub> (BGO), is used as a [[scintillator]].<ref name="BGO">{{cite journal |title=A Bismuth Germanate-Avalanche Photodiode Module Designed for Use in High Resolution Positron Emission Tomography |last=Lightstone |first=A. W. |author2=McIntyre, R. J. |author3=Lecomte, R. |author4=Schmitt, D. |journal=IEEE Transactions on Nuclear Science |date=1986 |volume=33 |issue=1 |pages=456–459 |doi=10.1109/TNS.1986.4337142 |bibcode=1986ITNS...33..456L |s2cid=682173}}</ref>

[[Binary compound]]s with other [[chalcogen]]s are also known, such as the [[Germanium disulfide|disulfide]] ({{chem|GeS|2}}) and [[Germanium diselenide|diselenide]] ({{chem|GeSe|2}}), and the [[germanium monosulfide|monosulfide]] (GeS), [[Germanium monoselenide|monoselenide]] (GeSe), and [[Germanium telluride|monotelluride]] (GeTe).<ref name = "Greenwood" /> GeS<sub>2</sub> forms as a white precipitate when hydrogen sulfide is passed through strongly acid solutions containing Ge(IV).<ref name = "Greenwood" /> The disulfide is appreciably soluble in water and in solutions of caustic alkalis or alkaline sulfides. Nevertheless, it is not soluble in acidic water, which allowed Winkler to discover the element.<ref>{{cite journal |first=Otto H. |last=Johnson |title=Germanium and its Inorganic Compounds |journal=Chem. Rev. |date=1952 |volume=51 |issue=3 |pages=431–469 |doi=10.1021/cr60160a002}}</ref> By heating the disulfide in a current of [[hydrogen]], the monosulfide (GeS) is formed, which sublimes in thin plates of a dark color and metallic luster, and is soluble in solutions of the caustic alkalis.<ref name="HollemanAF" /> Upon melting with [[alkali metal compound|alkaline carbonates]] and [[sulfur]], germanium compounds form salts known as thiogermanates.<ref>{{cite journal |doi=10.1039/a703634e |title=First synthesis of mesostructured thiogermanates |date=1997 |last1=Fröba |first1=Michael |journal=Chemical Communications |issue=18 |pages=1729–1730 |last2=Oberender |first2=Nadine}}</ref>

[[File:Germane-2D-dimensions.svg|class=skin-invert-image|upright|left|thumb|Germane is similar to [[methane]].|alt=Skeletal chemical structure of a tetrahedral molecule with germanium atom in its center bonded to four hydrogen atoms. The Ge–H distance is 152.51 picometers.]]
Four tetra[[halides]] are known. Under normal conditions [[Germanium(IV) iodide|germanium tetraiodide]] (GeI<sub>4</sub>) is a solid, [[germanium tetrafluoride]] (GeF<sub>4</sub>) a gas and the others volatile liquids. For example, [[germanium tetrachloride]], GeCl<sub>4</sub>, is obtained as a colorless fuming liquid boiling at 83.1&nbsp;°C by heating the metal with chlorine.<ref name="HollemanAF" /> All the tetrahalides are readily hydrolyzed to hydrated germanium dioxide.<ref name="HollemanAF" /> GeCl<sub>4</sub> is used in the production of organogermanium compounds.<ref name = "Greenwood" /> All four dihalides are known and in contrast to the tetrahalides are polymeric solids.<ref name = "Greenwood" /> Additionally Ge<sub>2</sub>Cl<sub>6</sub> and some higher compounds of formula Ge<sub>''n''</sub>Cl<sub>2''n''+2</sub> are known.<ref name="HollemanAF" /> The unusual compound Ge<sub>6</sub>Cl<sub>16</sub> has been prepared that contains the Ge<sub>5</sub>Cl<sub>12</sub> unit with a [[neopentane]] structure.<ref>{{cite journal |title=The Crystal Structure and Raman Spectrum of Ge<sub>5</sub>Cl<sub>12</sub>·GeCl<sub>4</sub> and the Vibrational Spectrum of Ge<sub>2</sub>Cl<sub>6</sub> |last1=Beattie |first1=I. R. |last2=Jones |first2=P.J. |last3=Reid |first3=G. |author4=Webster, M. |journal=Inorg. Chem. |volume=37 |issue=23 |pages=6032–6034 |date=1998 |doi=10.1021/ic9807341 |pmid=11670739}}</ref>

[[Germane]] (GeH<sub>4</sub>) is a compound similar in structure to [[methane]]. Polygermanes—compounds that are similar to [[alkane]]s—with formula Ge<sub>''n''</sub>H<sub>2''n''+2</sub> containing up to five germanium atoms are known.<ref name = "Greenwood" /> The germanes are less volatile and less reactive than their corresponding silicon analogues.<ref name = "Greenwood" /> GeH<sub>4</sub> reacts with alkali metals in liquid ammonia to form white crystalline MGeH<sub>3</sub> which contain the [[germyl|GeH<sub>3</sub><sup>−</sup>]] [[anion]].<ref name = "Greenwood" /> The germanium hydrohalides with one, two and three halogen atoms are colorless reactive liquids.<ref name = "Greenwood" />

[[File:NucleophilicAdditionWithOrganogermanium.png|class=skin-invert-image|right|thumb|upright=1.25|[[Nucleophile|Nucleophilic]] addition with an organogermanium compound|alt=Skeletal chemical structures outlining an additive chemical reaction including an organogermanium compound.]]
The first [[organogermanium compound]] was synthesized by Winkler in 1887; the reaction of germanium tetrachloride with [[diethylzinc]] yielded [[tetraethylgermane]] ({{chem|Ge(C|2|H|5|)|4}}).<ref name="Winkle2" /> Organogermanes of the type R<sub>4</sub>Ge (where R is an [[alkyl]]) such as [[tetramethylgermane]] ({{chem|Ge(CH|3|)|4}}) and tetraethylgermane are accessed through the cheapest available germanium precursor [[germanium tetrachloride]] and alkyl nucleophiles. Organic germanium hydrides such as [[isobutylgermane]] ({{chem|(CH|3|)|2|CHCH|2|GeH|3}}) were found to be less hazardous and may be used as a liquid substitute for toxic germane gas in [[semiconductor]] applications. Many germanium [[reactive intermediate]]s are known: [[-yl|germyl]] [[free radical]]s, [[germylene]]s (similar to [[carbene]]s), and germynes (similar to [[carbyne]]s).<ref>{{cite journal |title=Reactive intermediates in organogermanium chemistry |first=Jacques |last=Satge |journal=Pure Appl. Chem. |volume=56 |issue=1 |pages=137–150 |date=1984 |doi=10.1351/pac198456010137 |s2cid=96576323 |doi-access=free}}</ref><ref>{{cite journal |title=Organogermanium Chemistry |first=Denis |last=Quane |author2=Bottei, Rudolph S. |journal=Chemical Reviews |volume=63 |issue=4 |pages=403–442 |date=1963 |doi=10.1021/cr60224a004}}</ref> The organogermanium compound [[Propagermanium|2-carboxyethylgermasesquioxane]] was first reported in the 1970s, and for a while was used as a dietary supplement and thought to possibly have anti-tumor qualities.<ref name="toxic" />

Using a ligand called Eind (1,1,3,3,5,5,7,7-octaethyl-s-hydrindacen-4-yl) germanium is able to form a double bond with oxygen (germanone). Germanium hydride and germanium tetrahydride are very flammable and even explosive when mixed with air.<ref>{{cite news |last=Broadwith |first=Phillip |title=Germanium-oxygen double bond takes centre stage |url=http://www.rsc.org/chemistryworld/News/2012/March/germanone-germanium-oxygen-double-bond-created.asp |access-date=2014-05-15 |newspaper=Chemistry World |date=25 March 2012 |archive-date=2014-05-17 |archive-url=https://web.archive.org/web/20140517121351/http://www.rsc.org/chemistryworld/News/2012/March/germanone-germanium-oxygen-double-bond-created.asp |url-status=live}}</ref>

=== Isotopes ===
{{main|Isotopes of germanium}}
Germanium occurs in five natural [[isotope]]s: {{SimpleNuclide|Germanium|70}}, {{SimpleNuclide|Germanium|72}}, {{SimpleNuclide|Germanium|73}}, {{SimpleNuclide|Germanium|74}}, and {{SimpleNuclide|Germanium|76}}. Of these, {{SimpleNuclide|Germanium|76}} is very slightly radioactive, decaying by [[double beta decay]] with a [[half-life]] of {{val|1.78|e=21|u=years}}. {{SimpleNuclide|Germanium|74}} is the most common isotope, having a [[natural abundance]] of approximately 36%. {{SimpleNuclide|Germanium|76}} is the least common with a natural abundance of approximately 7%.<ref name="nubase">{{NUBASE 2003}}</ref> When bombarded with alpha particles, the isotope {{SimpleNuclide|Germanium|72}} will generate stable {{SimpleNuclide|Selenium|77|link=yes}}, releasing high energy electrons in the process.<ref name="72Ge" /> Because of this, it is used in combination with [[radon]] for [[Atomic battery|nuclear batteries]].<ref name="72Ge">Perreault, Bruce A. [https://patents.google.com/patent/US7800286 "Alpha Fusion Electrical Energy Valve"], US Patent 7800286, issued September 21, 2010. {{webarchive |url=https://web.archive.org/web/20071012103442/http://www.nuenergy.org/disclosures/AlphaFusionPatent_05-04-2007.pdf |archive-url=https://web.archive.org/web/20071012103442/http://www.nuenergy.org/disclosures/AlphaFusionPatent_05-04-2007.pdf |archive-date=2007-10-12 |url-status=live |date=October 12, 2007 |title=PDF copy }}</ref>

At least 27 [[radioisotope]]s have also been synthesized, ranging in atomic mass from 58 to 89. The most stable of these is {{SimpleNuclide|Germanium|68}}, decaying by [[electron capture]] with a half-life of {{val|270.95|u=days}}ays. The least stable is {{SimpleNuclide|Germanium|60}}, with a half-life of {{val|30|ul=ms}}. While most of germanium's radioisotopes decay by [[beta decay]], {{SimpleNuclide|Germanium|61}} and {{SimpleNuclide|Germanium|64}} decay by [[Positron emission|{{SubatomicParticle|beta+}}]] delayed [[proton emission]].<ref name="nubase" /> {{SimpleNuclide|Germanium|84}} through {{SimpleNuclide|Germanium|87}} isotopes also exhibit minor [[Beta decay|{{SubatomicParticle|beta-}}]] delayed [[neutron emission]] decay paths.<ref name="nubase" />

=== Occurrence ===
{{category see also|Germanium minerals}}
[[File:Renierit.JPG|thumb|[[Renierite]]|alt=A brown block of irregular shape and surface, about 6 cm in size.]]
Germanium is created by [[stellar nucleosynthesis]], mostly by the [[s-process]] in [[asymptotic giant branch]] stars. The s-process is a slow [[neutron]] capture of lighter elements inside pulsating [[red giant]] stars.<ref name="sterling">{{cite journal |journal=The Astrophysical Journal Letters |volume=578 |issue=1 |pages=L55–L58 |doi=10.1086/344473 |title=Discovery of Enhanced Germanium Abundances in Planetary Nebulae with the Far Ultraviolet Spectroscopic Explorer |first=N. C. |last=Sterling |author2=Dinerstein, Harriet L. |author3=Bowers, Charles W. |bibcode=2002ApJ...578L..55S |arxiv=astro-ph/0208516 |year=2002 |s2cid=119395123 |author2-link=Harriet Dinerstein}}</ref> Germanium has been detected in some of the most distant stars<ref>{{cite journal |journal=Nature |volume=423 |issue=29 |date=2003-05-01 |pmid=12721614 |doi=10.1038/423029a |title=Astronomy: Elements of surprise |last=Cowan |first=John |page=29 |bibcode=2003Natur.423...29C |s2cid=4330398 |doi-access=free}}</ref> and in the atmosphere of Jupiter.<ref>{{cite journal |title=The tropospheric gas composition of Jupiter's north equatorial belt /NH<sub>3</sub>, PH<sub>3</sub>, CH<sub>3</sub>D, GeH<sub>4</sub>, H<sub>2</sub>O/ and the Jovian D/H isotopic ratio |last=Kunde |first=V. |author2=Hanel, R. |author3=Maguire, W. |author4=Gautier, D. |author5=Baluteau, J. P. |author6=Marten, A. |author7=Chedin, A. |author8=Husson, N. |author9=Scott, N. |journal=Astrophysical Journal |volume=263 |date=1982 |pages=443–467 |doi=10.1086/160516 |bibcode=1982ApJ...263..443K}}</ref>

Germanium's abundance [[abundance of elements in Earth's crust|in the Earth's crust]] is approximately 1.6&nbsp;[[Parts per million|ppm]].<ref name="Holl">{{cite journal |doi=10.1016/j.oregeorev.2005.07.034 |title=Metallogenesis of germanium – A review |first=R. |last=Höll |author2=Kling, M. |author3=Schroll, E. |journal=Ore Geology Reviews |volume=30 |issue=3–4 |date=2007 |pages=145–180}}</ref> Only a few minerals like [[argyrodite]], [[briartite]], [[germanite]], [[renierite]] and [[sphalerite]] contain appreciable amounts of germanium.<ref name="usgs" /><ref>{{Cite journal |url=https://www.researchgate.net/publication/309583931 |title=The distribution of gallium, germanium and indium in conventional and non-conventional resources – Implications for global availability (PDF Download Available) |website=ResearchGate |doi=10.13140/rg.2.2.20956.18564 |access-date=2017-06-10 |last1=Frenzel |first1=Max |year=2016 |publisher=Unpublished |archive-date=2018-10-06 |archive-url=https://web.archive.org/web/20181006235214/https://www.researchgate.net/publication/309583931 |url-status=live}}</ref> Only few of them (especially germanite) are, very rarely, found in mineable amounts.<ref>{{cite journal |url=https://www.researchgate.net/publication/250273740 |title=Eyselite, Fe3+Ge34+O7(OH), a new mineral species from Tsumeb, Namibia |journal=The Canadian Mineralogist |volume=42 |issue=6 |pages=1771–1776 |date=December 2004 |doi=10.2113/gscanmin.42.6.1771 |first1=Andrew C. |last1=Roberts |bibcode=2004CaMin..42.1771R |display-authors=etal}}</ref><ref>{{Cite web |url=https://www.deutsche-rohstoffagentur.de/DERA/DE/Downloads/vortrag_germanium.pdf?__blob=publicationFile&v=2 |title=Archived copy |access-date=2018-10-06 |archive-date=2018-10-06 |archive-url=https://web.archive.org/web/20181006234914/https://www.deutsche-rohstoffagentur.de/DERA/DE/Downloads/vortrag_germanium.pdf?__blob=publicationFile&v=2 |url-status=live}}</ref><ref>{{Cite web |url=http://tupa.gtk.fi/raportti/arkisto/070_peh_76.pdf |title=Archived copy |access-date=2018-10-06 |archive-date=2020-03-20 |archive-url=https://web.archive.org/web/20200320190457/http://tupa.gtk.fi/raportti/arkisto/070_peh_76.pdf |url-status=live}}</ref><!--Ore found in the Pend Orielle Mine near [[Detroit]] has exceptionally high amounts of germanium.<ref>{{cite web |url=http://periodictable.com/Elements/032/index.html |title=Pictures, stories, and facts about the element Germanium in the Periodic Table |website=periodictable.com}}</ref><ref>{{Cite doi | 10.2307/30056827}}</ref>--> Some zinc–copper–lead ore bodies contain enough germanium to justify extraction from the final ore concentrate.<ref name="Holl" /> An unusual natural enrichment process causes a high content of germanium in some coal seams, discovered by [[Victor Moritz Goldschmidt]] during a broad survey for germanium deposits.<ref name="Gold1">{{cite journal |journal=Nachrichten von der Gesellschaft der Wissenschaften zu Göttingen, Mathematisch-Physikalische Klasse |title=Ueber das Vorkommen des Germaniums in Steinkohlen und Steinkohlenprodukten |last=Goldschmidt |first=V. M. |pages=141–167 |date=1930 |url=http://resolver.sub.uni-goettingen.de/purl?GDZPPN002508303 |access-date=2008-08-25 |archive-date=2018-03-03 |archive-url=https://web.archive.org/web/20180303165042/http://resolver.sub.uni-goettingen.de/purl?GDZPPN002508303 |url-status=live}}</ref><ref name="Gold2">{{cite journal |journal=Nachrichten von der Gesellschaft der Wissenschaften zu Göttingen, Mathematisch-Physikalische Klasse |title=Zur Geochemie des Germaniums |last=Goldschmidt |first=V. M. |author2=Peters, Cl. |pages=141–167 |url=http://resolver.sub.uni-goettingen.de/purl?GDZPPN002509180 |date=1933 |access-date=2008-08-25 |archive-date=2008-12-01 |archive-url=https://web.archive.org/web/20081201115130/http://resolver.sub.uni-goettingen.de/purl/?GDZPPN002509180 |url-status=live}}</ref> The highest concentration ever found was in [[Hartley, Northumberland|Hartley]] coal ash with as much as 1.6% germanium.<ref name="Gold1" /><ref name="Gold2" /> The coal deposits near [[Xilinhaote]], [[Inner Mongolia]], contain an estimated 1600&nbsp;[[tonne]]s of germanium.<ref name="Holl" />

== Production ==
About 118&nbsp;[[tonne]]s of germanium were produced in 2011 worldwide, mostly in China (80 t), Russia (5 t) and United States (3 t).<ref name="usgs" /> Germanium is recovered as a by-product from [[sphalerite]] zinc ores where it is concentrated in amounts as great as 0.3%,<ref>{{cite journal |doi=10.1016/0016-7037(85)90241-8 |title=Germanium geochemistry and mineralogy |date=1985 |last=Bernstein |first=L. |journal=Geochimica et Cosmochimica Acta |volume=49 |issue=11 |pages=2409–2422 |bibcode=1985GeCoA..49.2409B}}</ref> especially from low-temperature sediment-hosted, massive [[zinc|Zn]]–[[lead|Pb]]–[[copper|Cu]](–[[barium|Ba]]) deposits and carbonate-hosted Zn–Pb deposits.<ref>{{Cite journal |title=Gallium, germanium, indium and other minor and trace elements in sphalerite as a function of deposit type – A meta-analysis |last1=Frenzel |first1=Max |date=July 2016 |journal=Ore Geology Reviews |doi=10.1016/j.oregeorev.2015.12.017 |last2=Hirsch |first2=Tamino |last3=Gutzmer |first3=Jens |volume=76 |pages=52–78 |bibcode=2016OGRv...76...52F}}</ref> A recent study found that at least 10,000 t of extractable germanium is contained in known zinc reserves, particularly those hosted by [[Carbonate-hosted lead-zinc ore deposits|Mississippi-Valley type deposits]], while at least 112,000&nbsp;t will be found in coal reserves.<ref>{{multiref|{{Cite journal |title=On the geological availability of germanium |journal=Mineralium Deposita |date=2013-12-29 |issn=0026-4598 |pages=471–486 |volume=49 |issue=4 |doi=10.1007/s00126-013-0506-z |first1=Max |last1=Frenzel |first2=Marina P. |last2=Ketris |first3=Jens |last3=Gutzmer |bibcode=2014MinDe..49..471F |s2cid=129902592}}|{{Cite journal |title=Erratum to: On the geological availability of germanium |journal=Mineralium Deposita |date=2014-01-19 |issn=0026-4598 |page=487 |volume=49 |issue=4 |doi=10.1007/s00126-014-0509-4 |first1=Max |last1=Frenzel |first2=Marina P. |last2=Ketris |first3=Jens |last3=Gutzmer |bibcode=2014MinDe..49..487F |s2cid=140620827 |doi-access=free}}}}</ref> In 2007 35% of the demand was met by recycled germanium.<ref name="Holl" />

<div style="float: right; margin: 5px;">
{|class="wikitable" style="font-size:85%; text-align:right;"
!Year !! Cost<br />([[United States dollar|$]]/kg)<ref><!--two sources in one here?-->{{Cite book |title=USGS Minerals Information |url=http://minerals.usgs.gov/minerals/pubs/commodity/germanium/index.html#mcs |at=[http://minerals.usgs.gov/minerals/pubs/commodity/germanium/220303.pdf January 2003], [http://minerals.usgs.gov/minerals/pubs/commodity/germanium/germamcs04.pdf January 2004], [http://minerals.usgs.gov/minerals/pubs/commodity/germanium/germamcs05.pdf January 2005], [http://minerals.usgs.gov/minerals/pubs/commodity/germanium/germamcs06.pdf January 2006], [http://minerals.usgs.gov/minerals/pubs/commodity/germanium/germamcs07.pdf January 2007], [http://minerals.usgs.gov/minerals/pubs/commodity/germanium/mcs-2010-germa.pdf January 2010] |isbn=978-0-85934-039-7 |author=R.N. Soar |oclc=16437701 |date=1977 |publisher=Babani Press |access-date=2013-04-22 |archive-date=2013-05-07 |archive-url=https://web.archive.org/web/20130507125723/http://minerals.usgs.gov/minerals/pubs/commodity/germanium/index.html#mcs |url-status=live}}</ref>
|-
|1999 || 1,400
|-
|2000 || 1,250
|-
|2001 || 890
|-
|2002 || 620
|-
|2003 || 380
|-
|2004 || 600
|-
|2005 || 660
|-
|2006 || 880
|-
|2007 || 1,240
|-
|2008 || 1,490
|-
|2009 || 950
|-
|2010 || 940
|-
|2011 || 1,625
|-
|2012 || 1,680
|-
|2013 || 1,875
|-
|2014 || 1,900
|-
|2015 || 1,760
|-
|2016 || 950
|-
|2017 || 1,358
|-
|2018 || 1,300
|-
|2019 || 1,240
|-
|2020 || 1,000
|}
</div>
While it is produced mainly from [[sphalerite]], it is also found in [[silver]], [[lead]], and [[copper]] ores. Another source of germanium is [[fly ash]] of power plants fueled from coal deposits that contain germanium. Russia and China used this as a source for germanium.<ref name="Naumov">{{cite journal |first=A. V. |last=Naumov |title=World market of germanium and its prospects |journal=Russian Journal of Non-Ferrous Metals |volume=48 |issue=4 |date=2007 |doi=10.3103/S1067821207040049 |pages=265–272 |s2cid=137187498}}</ref> Russia's deposits are located in the far east of [[Sakhalin]] Island, and northeast of [[Vladivostok]]. The deposits in China are located mainly in the [[lignite]] mines near [[Lincang]], [[Yunnan]]; coal is also mined near [[Xilinhaote]], [[Inner Mongolia]].<ref name="Holl" />

The ore concentrates are mostly [[sulfide|sulfidic]]; they are converted to the [[oxide]]s by heating under air in a process known as [[Roasting (metallurgy)|roasting]]:

: GeS<sub>2</sub> + 3 O<sub>2</sub> → GeO<sub>2</sub> + 2 SO<sub>2</sub>

Some of the germanium is left in the dust produced, while the rest is converted to germanates, which are then leached (together with zinc) from the cinder by sulfuric acid. After neutralization, only the zinc stays in solution while germanium and other metals precipitate. After removing some of the zinc in the precipitate by the [[Waelz process]], the residing Waelz oxide is leached a second time. The [[germanium dioxide|dioxide]] is obtained as precipitate and converted with [[chlorine]] gas or hydrochloric acid to [[germanium tetrachloride]], which has a low boiling point and can be isolated by distillation:<ref name="Naumov" />

: GeO<sub>2</sub> + 4 HCl → GeCl<sub>4</sub> + 2 H<sub>2</sub>O
: GeO<sub>2</sub> + 2 Cl<sub>2</sub> → GeCl<sub>4</sub> + O<sub>2</sub>

Germanium tetrachloride is either hydrolyzed to the oxide (GeO<sub>2</sub>) or purified by fractional distillation and then hydrolyzed.<ref name="Naumov" /> The highly pure GeO<sub>2</sub> is now suitable for the production of germanium glass. It is reduced to the element by reacting it with hydrogen, producing germanium suitable for infrared optics and semiconductor production:

: GeO<sub>2</sub> + 2 H<sub>2</sub> → Ge + 2 H<sub>2</sub>O

The germanium for steel production and other industrial processes is normally reduced using carbon:<ref name="Moska">{{cite journal |journal=Minerals Engineering |date=2004 |pages=393–402 |doi=10.1016/j.mineng.2003.11.014 |title=Review of germanium processing worldwide |issue=3 |author=Moskalyk, R. R. |volume=17 |bibcode=2004MiEng..17..393M}}</ref>

: GeO<sub>2</sub> + C → Ge + CO<sub>2</sub>

== Applications ==
The major global end uses for germanium were electronics and solar applications, fiber-optic systems, infrared optics, and polymerization catalysts. Other uses included chemotherapy, metallurgy, and phosphors.<ref>{{Cite web |last=Mineral |first=Commodity |date=January 4, 2024 |title=Mineral Commodity Summaries 2024 |url=https://pubs.usgs.gov/periodicals/mcs2024/mcs2024-germanium.pdf |access-date=May 14, 2025 |website=Mineral Commodity}}</ref>

=== Optics ===
[[File:Singlemode fibre structure.svg|thumb|right|upright=.65|alt=A drawing of four concentric cylinders.|A typical single-mode optical fiber. Germanium oxide is a [[dopant]] of the core silica (Item 1). {{olist
    |Core 8&nbsp;µm
    |Cladding 125&nbsp;µm
    |Buffer 250&nbsp;µm
    |Jacket 400&nbsp;µm
}}]]
The notable properties of [[Germanium dioxide|germania]] (GeO<sub>2</sub>) are its high [[refractive index|index of refraction]] and its low [[Dispersion (optics)|optical dispersion]]. These make it especially useful for [[wide-angle camera lens]]es, [[microscopy]], and the core part of [[optical fiber]]s.<ref>{{cite journal |title=Infrared Detector Arrays for Astronomy |journal=Annual Review of Astronomy and Astrophysics |date=2007 |doi=10.1146/annurev.astro.44.051905.092436 |last=Rieke |first=G. H. |s2cid=26285029 |volume=45 |issue=1 |pages=77–115 |bibcode=2007ARA&A..45...77R}}</ref><ref name="Brown">{{cite web |url=http://minerals.usgs.gov/minerals/pubs/commodity/germanium/220400.pdf |title=Germanium |first=Robert D. Jr. |last=Brown |publisher=U.S. Geological Survey |year=2000 |access-date=2008-09-22 |archive-date=2011-06-08 |archive-url=https://web.archive.org/web/20110608071221/http://minerals.usgs.gov/minerals/pubs/commodity/germanium/220400.pdf |url-status=live}}</ref> It has replaced [[titanium dioxide|titania]] as the [[dopant]] for silica fiber, eliminating the subsequent heat treatment that made the fibers brittle.<ref>{{cite web |url=http://ptgmedia.pearsoncmg.com/images/1587051052/samplechapter/1587051052content.pdf |title=Chapter III: Optical Fiber For Communications |publisher=Stanford Research Institute |access-date=2008-08-22 |archive-date=2014-12-05 |archive-url=https://web.archive.org/web/20141205210827/http://ptgmedia.pearsoncmg.com/images/1587051052/samplechapter/1587051052content.pdf |url-status=live}}</ref> At the end of 2002, the fiber optics industry consumed 60% of the annual germanium use in the United States, but this is less than 10% of worldwide consumption.<ref name="Brown" /> [[GeSbTe]] is a [[phase change material]] used for its optic properties, such as that used in [[DVD-RW|rewritable DVDs]].<ref>{{cite web |url=http://www.osta.org/technology/pdf/dvdqa.pdf |archive-url=https://web.archive.org/web/20090419202545/http://www.osta.org/technology/pdf/dvdqa.pdf |archive-date=2009-04-19 |title=Understanding Recordable & Rewritable DVD |edition=First |access-date=2008-09-22 |publisher=Optical Storage Technology Association (OSTA)}}</ref>

Because germanium is transparent in the infrared wavelengths, it is an important [[infrared]] optical material that can be readily cut and polished into lenses and windows. It is especially used as the front optic in [[Thermographic camera|thermal imaging cameras]] working in the 8 to 14&nbsp;[[micrometre|micron]] range for passive thermal imaging and for hot-spot detection in military, mobile [[night vision]], and fire fighting applications.<ref name="Moska" /> It is used in infrared [[spectroscope]]s and other optical equipment that require extremely sensitive [[thermography|infrared detectors]].<ref name="Brown" /> It has a very high [[refractive index]] (4.0) and must be coated with anti-reflection agents. Particularly, a very hard special antireflection coating of [[diamond-like carbon]] (DLC), refractive index 2.0, is a good match and produces a diamond-hard surface that can withstand much environmental abuse.<ref>{{cite journal |first=Alan H. |last=Lettington |doi=10.1016/S0008-6223(98)00062-1 |title=Applications of diamond-like carbon thin films |volume=36 |issue=5–6 |date=1998 |pages=555–560 |journal=Carbon |bibcode=1998Carbo..36..555L}}</ref><ref>{{cite journal |first=Michael N. |last=Gardos |author2=Bonnie L. Soriano |author3=Steven H. Propst |title=Study on correlating rain erosion resistance with sliding abrasion resistance of DLC on germanium |journal=Proc. SPIE |volume=1325 |page=99 |date=1990 |doi=10.1117/12.22449 |issue=Mechanical Properties |series=SPIE Proceedings |editor1-last=Feldman |editor1-first=Albert |editor2-last=Holly |editor2-first=Sandor |bibcode=1990SPIE.1325...99G |s2cid=137425193}}</ref>

=== Electronics ===
Germanium can be alloyed with [[silicon]], and [[silicon–germanium]] alloys are rapidly becoming an important semiconductor material for high-speed integrated circuits. Circuits using the properties of Si-SiGe [[heterojunction]]s can be much faster than those using silicon alone.<ref>{{cite journal |doi=10.1109/TED.2003.810484 |title=SiGe HBT and BiCMOS technologies for optical transmission and wireless communication systems |date=2003 |last=Washio |first=K. |journal=IEEE Transactions on Electron Devices |volume=50 |issue=3 |pages=656–668 |bibcode=2003ITED...50..656W}}</ref> The SiGe chips, with high-speed properties, can be made with low-cost, well-established production techniques of the [[silicon chip]] industry.<ref name="usgs" />

High efficiency [[solar panel]]s are a major use of germanium. Because germanium and [[gallium arsenide]] have nearly identical [[lattice constant]], germanium substrates can be used to make gallium-arsenide [[solar cell]]s.<ref>{{cite journal |doi=10.1002/pip.446 |title=Space and terrestrial photovoltaics: synergy and diversity |date=2002 |last1=Bailey |first1=Sheila G. |journal=Progress in Photovoltaics: Research and Applications |volume=10 |issue=6 |pages=399–406 |last2=Raffaelle |first2=Ryne |last3=Emery |first3=Keith |hdl=2060/20030000611 |bibcode=2002sprt.conf..202B |s2cid=98370426 |hdl-access=free}}</ref> Germanium is the substrate of the wafers for high-efficiency [[multijunction photovoltaic cell]]s for space applications, such as the [[Mars Exploration Rover]]s, which use triple-junction gallium arsenide on germanium cells.<ref>{{cite journal |doi=10.1016/S0094-5765(02)00287-4 |title=The performance of gallium arsenide/germanium solar cells at the Martian surface |date=January 2004 |first=D. |last=Crisp |author2=Pathare, A. |author3=Ewell, R. C. |journal=Acta Astronautica |volume=54 |issue=2 |pages=83–101 |bibcode=2004AcAau..54...83C}}</ref> High-brightness LEDs, used for automobile headlights and to backlight LCD screens, are also an important application.<ref name="usgs" />

Germanium-on-insulator (GeOI) substrates are seen as a potential replacement for silicon on miniaturized chips.<ref name="usgs" /> CMOS circuit based on GeOI substrates has been reported recently.<ref>{{cite journal |first1=Heng |last1=Wu |first2=Peide D. |last2=Ye |date=August 2016 |title=Fully Depleted Ge CMOS Devices and Logic Circuits on Si |journal=[[IEEE Transactions on Electron Devices]] |volume=63 |issue=8 |pages=3028–3035 |doi=10.1109/TED.2016.2581203 |bibcode=2016ITED...63.3028W |s2cid=3231511 |url=https://engineering.purdue.edu/~yep/Papers/TED_Ge%20Fully%20Depleted%20CMOS_2016.pdf |access-date=2019-03-04 |archive-date=2019-03-06 |archive-url=https://web.archive.org/web/20190306044456/https://engineering.purdue.edu/~yep/Papers/TED_Ge%20Fully%20Depleted%20CMOS_2016.pdf |url-status=live}}</ref> Other uses in electronics include [[phosphor]]s in [[fluorescent lamp]]s<ref name="lanl" /> and solid-state light-emitting diodes (LEDs).<ref name="usgs" /> Germanium transistors are still used in some [[effects pedal]]s by musicians who wish to reproduce the distinctive tonal character of the [[Distortion (music)|"fuzz"-tone]] from the early [[rock and roll]] era, most notably the [[Fuzz Face|Dallas Arbiter Fuzz Face]].<ref>{{cite journal |author=Szweda, Roy |date=2005 |title=Germanium phoenix |journal=[[III-Vs Review]] |volume=18 |issue=7 |page=55 |doi=10.1016/S0961-1290(05)71310-7}}</ref>

Germanium has been studied as a potential material for implantable bioelectronic sensors that are [[Biodegradable electronics|resorbed]] in the body without generating harmful hydrogen gas, replacing [[zinc oxide]]- and [[indium gallium zinc oxide]]-based implementations.<ref>{{ cite journal |last1=Zhao |first1=H. |last2=Xue |first2=Z. |last3=Wu |first3=X. |display-authors=2 |date=21 July 2022 |title=Biodegradable germanium electronics for integrated biosensing of physiological signals. |journal=npj Flexible Electronics |volume=6 |at=63 |doi=10.1038/s41528-022-00196-2 |s2cid=250702946 |doi-access=free}}</ref>

Germanium was also used to create many of the circuits found in some of the very first pieces of electronic musical gear, initially 1950s, primarily in early transistor-based circuits. The first guitar effects pedals in the 1960s – Fuzz pedals like the Maestro FZ-1 (1962), Dallas-Arbiter Fuzz Face (1966), and Tone Bender (1965) - used germanium transistors.<ref>{{Cite web |last=joe |date=2012-01-03 |title=The Germanium Mystique |url=https://tonefiend.com/diy/the-germanium-mystique/ |access-date=2025-02-21 |website=tonefiend.com |language=en-US}}</ref> Silicon diodes are more frequently used in more modern equipment, but germanium diodes are still used in some applications as they have lower barrier potential and smoother [[transconductance]] curves, leading to less harsh [[Clipping (audio)|clipping]].<ref>{{Citation |last=Dailey |first=Denton J. |title=Guitar Effects Circuits |date=2013 |work=Electronics for Guitarists |pages=199–200 |url=https://link.springer.com/chapter/10.1007/978-1-4614-4087-1_5 |access-date=2025-02-21 |place=New York, NY |publisher=Springer New York |language=en |doi=10.1007/978-1-4614-4087-1_5 |isbn=978-1-4614-4086-4}}</ref>

=== Other uses ===
[[File:Pet Flasche.JPG|thumb|upright|A [[polyethylene terephthalate|PET]] [[bottle]]|alt=Photo of a standard transparent plastic bottle.]]
Germanium dioxide is also used in [[catalyst]]s for [[polymerization]] in the production of [[polyethylene terephthalate]] (PET).<ref name="Thiele">{{cite journal |last=Thiele |first=Ulrich K. |date=2001 |title=The Current Status of Catalysis and Catalyst Development for the Industrial Process of Poly(ethylene terephthalate) Polycondensation |journal=International Journal of Polymeric Materials |volume=50 |issue=3 |pages=387–394 |doi=10.1080/00914030108035115 |s2cid=98758568}}</ref> The high brilliance of this polyester is especially favored for PET bottles marketed in Japan.<ref name="Thiele" /> In the United States, germanium is not used for polymerization catalysts.<ref name="usgs" />

Due to the similarity between silica (SiO<sub>2</sub>) and germanium dioxide (GeO<sub>2</sub>), the silica stationary phase in some [[gas chromatography]] columns can be replaced by GeO<sub>2</sub>.<ref>{{cite journal |title=Germania-Based, Sol-Gel Hybrid Organic-Inorganic Coatings for Capillary Microextraction and Gas Chromatography |last1=Fang |first1=Li |last2=Kulkarni |first2=Sameer |last3=Alhooshani |first3=Khalid |last4=Malik |first4=Abdul |journal=Anal. Chem. |volume=79 |issue=24 |pages=9441–9451 |date=2007 |doi=10.1021/ac071056f |pmid=17994707}}</ref>

In recent years germanium has seen increasing use in precious metal alloys. In [[sterling silver]] alloys, for instance, it reduces [[firescale]], increases tarnish resistance, and improves precipitation hardening. A tarnish-proof silver alloy trademarked [[Argentium sterling silver|Argentium]] contains 1.2% germanium.<ref name="usgs" />

[[Semiconductor detector#Germanium detectors|Semiconductor detectors]] made of single crystal high-purity germanium can precisely identify radiation sources—for example in airport security.<ref>{{cite web |title=Performance of Light-Weight, Battery-Operated, High Purity Germanium Detectors for Field Use |first1=Ronald |last1=Keyser |last2=Twomey |first2=Timothy |last3=Upp |first3=Daniel |url=http://www.ortec-online.com/papers/inmm_2003_keyser.pdf |access-date=2008-09-06 |publisher=Oak Ridge Technical Enterprise Corporation (ORTEC) |archive-url=https://web.archive.org/web/20071026162911/http://www.ortec-online.com/papers/inmm_2003_keyser.pdf |archive-date=October 26, 2007 |url-status=dead}}</ref> Germanium is useful for [[Crystal monochromator|monochromators]] for [[beamline]]s used in [[single crystal]] [[neutron scattering]] and [[Synchrotron light|synchrotron X-ray]] diffraction. The reflectivity has advantages over silicon in neutron and [[High energy X-rays|high energy X-ray]] applications.<ref>{{cite journal |doi=10.1142/S0218301396000062 |date=1996 |journal=International Journal of Modern Physics E |volume=5 |issue=1 |pages=131–151 |title=Optimization of Germanium for Neutron Diffractometers |bibcode=1996IJMPE...5..131A |last1=Ahmed |first1=F. U. |last2=Yunus |first2=S. M. |last3=Kamal |first3=I. |last4=Begum |first4=S. |last5=Khan |first5=Aysha A. |last6=Ahsan |first6=M. H. |last7=Ahmad |first7=A. A. Z.}}</ref> Crystals of high purity germanium are used in detectors for [[gamma spectroscopy]] and the search for [[dark matter]].<ref>{{cite journal |doi=10.1016/j.nuclphysa.2005.02.155 |title=Astrophysical constraints from gamma-ray spectroscopy |date=2006 |last1=Diehl |first1=R. |journal=Nuclear Physics A |volume=777 |issue=2006 |pages=70–97 |last2=Prantzos |first2=N. |last3=Vonballmoos |first3=P. |arxiv=astro-ph/0502324 |bibcode=2006NuPhA.777...70D |citeseerx=10.1.1.256.9318 |s2cid=2360391}}</ref> Germanium crystals are also used in X-ray spectrometers for the determination of phosphorus, chlorine and sulfur.<ref>Eugene P. Bertin (1970). ''Principles and practice of X-ray spectrometric analysis'', Chapter 5.4 – Analyzer crystals, Table 5.1, p. 123; Plenum Press</ref>

Germanium is emerging as an important material for [[spintronics]] and spin-based [[quantum computing]] applications. In 2010, researchers demonstrated room temperature spin transport<ref>{{Cite journal |last1=Shen |first1=C. |last2=Trypiniotis |first2=T. |last3=Lee |first3=K. Y. |last4=Holmes |first4=S. N. |last5=Mansell |first5=R. |last6=Husain |first6=M. |last7=Shah |first7=V. |last8=Li |first8=X. V. |last9=Kurebayashi |first9=H. |date=2010-10-18 |title=Spin transport in germanium at room temperature |journal=Applied Physics Letters |volume=97 |issue=16 |page=162104 |doi=10.1063/1.3505337 |issn=0003-6951 |bibcode=2010ApPhL..97p2104S |url=https://eprints.soton.ac.uk/271616/1/Gespin.pdf |access-date=2018-11-16 |archive-date=2017-09-22 |archive-url=https://web.archive.org/web/20170922180043/https://eprints.soton.ac.uk/271616/1/Gespin.pdf |url-status=live}}</ref> and more recently donor electron spins in germanium has been shown to have very long [[coherence time]]s.<ref>{{Cite journal |last1=Sigillito |first1=A. J. |last2=Jock |first2=R. M. |last3=Tyryshkin |first3=A. M. |last4=Beeman |first4=J. W. |last5=Haller |first5=E. E. |last6=Itoh |first6=K. M. |last7=Lyon |first7=S. A. |date=2015-12-07 |title=Electron Spin Coherence of Shallow Donors in Natural and Isotopically Enriched Germanium |journal=Physical Review Letters |volume=115 |issue=24 |pages=247601 |doi=10.1103/PhysRevLett.115.247601 |pmid=26705654 |arxiv=1506.05767 |bibcode=2015PhRvL.115x7601S |s2cid=13299377}}</ref>

== Germanium and health ==
Germanium is not considered essential to the health of plants or animals.<ref name="American Cancer Society" /> Germanium in the environment has little or no health impact. This is primarily because it usually occurs only as a trace element in ores and [[carbon]]aceous materials, and the various industrial and electronic applications involve very small quantities that are not likely to be ingested.<ref name="usgs" /> For similar reasons, end-use germanium has little impact on the environment as a biohazard. Some reactive intermediate compounds of germanium are poisonous (see precautions, below).<ref name="Brown Jr">{{cite report |url=http://minerals.usgs.gov/minerals/pubs/commodity/germanium/220798.pdf |publisher=US Geological Surveys |access-date=2008-09-09 |title=Commodity Survey:Germanium |first=Robert D. Jr. |last=Brown |date= |archive-date=2018-03-04 |archive-url=https://web.archive.org/web/20180304113236/https://minerals.usgs.gov/minerals/pubs/commodity/germanium/220798.pdf |url-status=live}}</ref>

Germanium supplements, made from both organic and inorganic germanium, have been marketed as an [[alternative medicine]] capable of treating [[leukemia]] and [[lung cancer]].<ref name="acs" /> There is, however, no [[evidence-based medicine|medical evidence]] of benefit; some evidence suggests that such supplements are actively harmful.<ref name="American Cancer Society">{{cite book |publisher=American Cancer Society |title=American Cancer Society Complete Guide to Complementary and Alternative Cancer Therapies |edition=2nd |year=2009 |isbn=978-0944235713 |editor=Ades TB |pages=[https://archive.org/details/americancancerso0000unse/page/360 360–363] |chapter=Germanium |chapter-url=https://archive.org/details/americancancerso0000unse/page/360}}</ref> [[U.S. Food and Drug Administration]] (FDA) research has concluded that inorganic germanium, when used as a [[nutritional supplement]], "presents potential human [[health hazard]]".<ref name="toxic">{{cite journal |last=Tao |first=S. H. |author2=Bolger, P. M. |date=June 1997 |title=Hazard Assessment of Germanium Supplements |journal=[[Regulatory Toxicology and Pharmacology]] |volume=25 |issue=3 |pages=211–219 |doi=10.1006/rtph.1997.1098 |pmid=9237323 |url=https://zenodo.org/record/1229957 |access-date=2019-06-30 |archive-date=2020-03-10 |archive-url=https://web.archive.org/web/20200310041729/https://zenodo.org/record/1229957 |url-status=live}}</ref>

Some germanium compounds have been administered by alternative medical practitioners as non-FDA-allowed injectable solutions. Soluble inorganic forms of germanium used at first, notably the citrate-lactate salt, resulted in some cases of [[renal]] dysfunction, [[hepatic steatosis]], and peripheral [[neuropathy]] in individuals using them over a long term. Plasma and urine germanium concentrations in these individuals, several of whom died, were several orders of magnitude greater than [[endogenous]] levels. A more recent organic form, beta-carboxyethylgermanium sesquioxide ([[propagermanium]]), has not exhibited the same spectrum of toxic effects.<ref>{{cite book |author=Baselt, R. |title=Disposition of Toxic Drugs and Chemicals in Man |edition=8th |publisher=Biomedical Publications |place=Foster City, CA |date=2008 |pages=693–694}}</ref>

Certain compounds of germanium have low toxicity to [[mammal]]s, but have toxic effects against certain [[bacterium|bacteria]].<ref name="nbb">{{cite book |last=Emsley |first=John |title=Nature's Building Blocks |publisher=Oxford University Press |date=2001 |location=Oxford |pages=506–510 |isbn=978-0-19-850341-5}}</ref>

=== Precautions for chemically reactive germanium compounds ===
While use of germanium itself does not require precautions, some of germanium's artificially produced compounds are quite reactive and present an immediate hazard to human health on exposure. For example, [[Germanium tetrachloride]] and [[germane]] (GeH<sub>4</sub>) are a liquid and gas, respectively, that can be very irritating to the eyes, skin, lungs, and throat.<ref name="Gerber 1997 141–146">{{cite journal |first=G. B. |last=Gerber |author2=Léonard, A. |date=1997 |title=Mutagenicity, carcinogenicity and teratogenicity of germanium compounds |journal=Regulatory Toxicology and Pharmacology |volume=387 |issue=3 |pages=141–146 |doi=10.1016/S1383-5742(97)00034-3 |pmid=9439710 |bibcode=1997MRRMR.387..141G}}</ref>

== See also ==
* [[Germanene]]
* [[Vitrain]]
* [[History of the transistor]]

== Notes ==
{{NoteFoot}}

== References ==
{{Reflist}}

== External links ==
{{EB1911 poster|Germanium}}
* [http://www.periodicvideos.com/videos/032.htm Germanium] at ''[[The Periodic Table of Videos]]'' (University of Nottingham)

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