Editing Germanium (section)

== 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" />