Editing Titanite

{{Short description|Nesosilicate mineral}}
{{Redirect-distinguish|Sphene|Sphere}}
{{Infobox mineral
| name        = Titanite (Sphene)
| category    = [[silicate mineral|Nesosilicate]]
| boxwidth    = 
| image       = Titanite crystals on Amphibole - Ochtendung, Eifel, Germany.jpg
| imagesize   = 260px
| caption     = Titanite crystals on [[amphibole]] (image width 2 mm)
| formula     = {{chem2|CaTiSiO5}}
| IMAsymbol   = Ttn<ref>{{cite journal |last=Warr|first=L. N. |date=2021 |title=IMA–CNMNC approved mineral symbols |journal=[[Mineralogical Magazine]] |volume=85 |issue=3 |pages=291–320 |doi=10.1180/mgm.2021.43 |bibcode=2021MinM...85..291W |s2cid=235729616 |doi-access=free}}</ref>
| strunz      = 9.AG.15
| system      = [[Monoclinic]]
| class       = Prismatic (2/m) <br /><small>(same [[Hermann–Mauguin notation|H–M symbol]])</small>
| symmetry    = ''P''2<sub>1</sub>/a
| unit cell   = a = 7.057&nbsp;[[Ångström|Å]], b = 8.707&nbsp;Å <br />c = 6.555&nbsp;Å; β = 113.81°; Z&nbsp;=&nbsp;4
| colour      = Reddish brown, brown, gray, black, yellow, green, or red, colourless 
| habit       = Flattened wedge-shaped crystals, also massive
| twinning    = Contact and penetration on {100}, lamellar on {221}
| cleavage    = Distinct on [110], parting on {221}
| fracture    = Sub-[[conchoidal fracture|conchoidal]]
| tenacity    =
| mohs        = 5–5.5
| luster      = Sub-adamantine tending to slightly resinous
| streak      = Reddish white
| diaphaneity = Translucent to transparent
| gravity     = 3.48–3.60
| density     = 
| polish      = 
| opticalprop = Biaxial (+); very high [[optical relief|relief]]
| refractive  = nα = 1.843–1.950<br>nβ = 1.870–2.034 <br>nγ = 1.943–2.110
| birefringence = δ = 0.100–0.160 
| pleochroism = Strong: X = nearly colorless; Y = yellow to green; Z = red to yellow-orange
| 2V          = 17–40° (measured)
| dispersion  = r > v strong
| extinction  = 
| length fast/slow =
| fluorescence= 
| absorption  =
| melt        = 
| fusibility  = 
| diagnostic  = 
| solubility  = 
| other       = [[File:Radioactive.svg|25px]] [[Radioactive]] – may be metamict 
| alteration  = 
| references  =<ref name=Handbook>{{cite book |url=http://rruff.geo.arizona.edu/doclib/hom/titanite.pdf |title=Handbook of Mineralogy |chapter=Titanite}}</ref><ref name=Webmin>{{WebMineral |url=https://webmineral.com/data/Titanite.shtml |title=Titanite Mineral Data}}</ref><ref name=Mindat>{{Mindat|id=3977|name=Titanite}}</ref><ref name="Dana">{{cite book |last1=Dana|first1=James Dwight |author1-link=James Dwight Dana |last2=Ford|first2= William Ebenezer |title=Dana's Manual of Mineralogy for the Student of Elementary Mineralogy, the Mining Engineer, the Geologist, the Prospector, the Collector, Etc. |year=1915 |edition=13 |url=https://archive.org/details/danasmanualmine00fordgoog |access-date=2009-07-06 |publisher=[[Wiley (publisher)|John Wiley & Sons, Inc.]] |pages=[https://archive.org/details/danasmanualmine00fordgoog/page/n408 299]–300}}</ref>
}}
[[File:Titanite01.gif|thumb|Titanite crystal model]]

'''Titanite''', or '''sphene''' ({{etymology|grc|''{{Wikt-lang|grc|σφηνώ}}'' ({{grc-transl|σφηνώ}})|wedge}}),<ref name="Dana"/> is a [[calcium]] [[titanium]] [[silicate mineral|nesosilicate]] [[mineral]], [[calcium|Ca]][[titanium|Ti]][[silicon|Si]][[oxygen|O]]<sub>5</sub>. Trace impurities of [[iron]] and [[aluminium]] are typically present. Also commonly present are [[Rare earth element|rare earth]] metals including [[cerium]] and [[yttrium]]; calcium may be partly replaced by [[thorium]].<ref>{{Cite book |last1=Deer |first1=W. A.|last2=Howie |first2=R. A. |last3=Zussman |first3=J. |year=1966 |pages=17–20 |title=Introduction to the Rock-Forming Minerals |publisher=Longman |isbn=0-582-44210-9}}</ref>

==Nomenclature==
The [[International Mineralogical Association]] Commission on New Minerals and Mineral Names (CNMMN) adopted the name titanite and "discredited" the name sphene<ref>{{cite web|first1=Ernest H. |last1=Nickel |first2=Monte C. |last2=Nichols |author-link1=Ernest Henry Nickel |author-link2=Monte C. Nichols |url=http://pubsites.uws.edu.au/ima-cnmnc/IMA2008-10.pdf#page=280 |title=IMA/CNMNC List of Mineral Names |date=2008-10-17 |page=280 |format=PDF |publisher=Material Data, Inc. |access-date=2009-03-14}}</ref> as of 1982,<ref>{{cite journal |title=International Mineralogical Association: Commission on New Minerals and Mineral Names |first=M. H. |last=Hey |journal=Mineralogical Magazine |date=December 1982 |volume=46 |issue=341 |pages=513–514 |doi=10.1180/minmag.1982.046.341.25|bibcode=1982MinM...46..513H |s2cid=140202196 }}</ref> although commonly papers and books initially identify the mineral using both names.<ref>{{cite book |title=Minerals: Their Constitution and Origin  |first1=Hans-Rudolf |last1=Wenk |first2=Andrei |last2=Bulakh |publisher=Cambridge University Press |date=May 2004 |isbn=978-0-521-52958-7 |location=New York, NY}}</ref><ref>{{cite book |title=Introduction to Optical Mineralogy |first =William D. |last=Nesse |publisher=Oxford University Press, USA |isbn=978-0-19-514910-4 |date=August 2003 |location=New York, NY}}</ref> Sphene was the most commonly used name until the IMA decision, although both were well known.<ref name="Dana"/> Some authorities<ref name="Hayden">{{cite journal |title=A thermobarometer for sphene (titanite) |first1=L. A. |last1=Hayden |first2=E. B. |last2=Watson |first3=D. A. |last3=Wark |journal=Contributions to Mineralogy and Petrology |year=2008 |volume=155 |issue=4 |pages=529–540 |doi=10.1007/s00410-007-0256-y|bibcode = 2008CoMP..155..529H |s2cid=129085138 }}</ref> think it is less confusing as the word is used to describe any chemical or crystal with [[Oxide|oxidized]] titanium such as the [[Rare earth element|rare earth]] titanate [[pyrochlore]]s series<ref>{{cite journal |title=Formation enthalpies of rare earth titanate pyrochlores |volume=177 |issue=6 |date=June 2004 |pages=1858–1866 |doi=10.1016/j.jssc.2004.01.009  |first1=K. B. |last1=Helean |first2=S. V. |last2=Ushakov |first3=C. E. |last3=Brown |first4=A.|last4=Navrotsky |first5=J. |last5=Lian |first6=R. C. |last6=Ewing |first7=J. M. |last7=Farmer |first8=L. A. |last8=Boatner |journal=Journal of Solid State Chemistry|bibcode = 2004JSSCh.177.1858H |s2cid=97381935 }}</ref> and many of the minerals with the [[Perovskite (structure)|perovskite structure]].<ref>{{cite journal |title=Luminescence in semi-crystalline zirconium titanate doped with lanthanum |volume=434 |issue=1–2 |date=October 2006 |pages=19–22 |journal=Materials Science and Engineering: A |first1=G. F. G. |last1=Freitas |first2=R. S. |last2=Nasar |first3=M. |last3=Cerqueira |first4=D. M. A. |last4=Melo |first5=E. |last5=Longo |first6=J. A. |last6=Varela |doi=10.1016/j.msea.2006.07.023}}</ref> The name sphene continues to be publishable in peer-reviewed scientific literature, e.g. a paper by Hayden et al. was published in early 2008 in the journal Contributions to Mineralogy and Petrology.<ref name="Hayden"/> Sphene persists as the informal name for titanite [[gemstone]]s.

==Physical properties==
[[Image:Titanite - Tormiq valley, Haramosh Mts, Pakistan.jpg|thumb|left|Green titanite crystal cluster from the Tormiq Valley, Haramosh Mountains, Pakistan]]
Titanite, which is named for its titanium content, occurs as translucent to transparent, reddish brown, gray, yellow, green, or red [[monoclinic]] [[crystal]]s. These crystals are typically [[Sphenoid (geometry)|sphenoid]] in [[crystal habit|habit]] and are often twinned. Possessing a subadamantine tending to slightly resinous [[lustre (mineralogy)|luster]], titanite has a [[Mohs scale of mineral hardness|hardness]] of 5.5 and a weak [[Cleavage (crystal)|cleavage]]. Its [[specific gravity]] varies between 3.52 and 3.54. Titanite's [[refractive index]] is 1.885–1.990 to 1.915–2.050 with a strong [[birefringence]] of 0.105 to 0.135 (biaxial positive); under the microscope this leads to a distinctive high relief which combined with the common yellow-brown colour and lozenge-shape cross-section makes the mineral easy to identify. Transparent specimens are noted for their strong [[pleochroism|trichroism]], the three colours presented being dependent on body colour. Owing to the [[Quenching (fluorescence)|quenching]] effect of iron, sphene exhibits no [[fluorescence]] under ultraviolet light. Some titanite has been found to be [[metamictization|metamict]], in consequence of structural damage due to radioactive decomposition of the often significant thorium content. When viewed in [[thin section]] with a [[petrographic microscope]], [[pleochroic halo]]s can be observed in minerals surrounding a titanite crystal.

==Occurrence==
Titanite occurs as a common accessory mineral in intermediate and [[felsic]] [[igneous rock]]s and associated [[pegmatite]]s. It also occurs in [[metamorphic rock]]s such as [[gneiss]] and [[schist]]s and [[skarn]]s.<ref name=Handbook/> Source localities include: Pakistan; Italy; Russia; China; Brazil; [[Tujetsch]], [[Gotthard Pass|St. Gothard]], Switzerland;<ref name="Dana"/> [[Madagascar]]; [[Tyrol (state)|Tyrol]], Austria; [[Renfrew County, Ontario]], Canada; [[Sanford, Maine|Sanford]], [[Maine]], [[Gouverneur (village), New York|Gouverneur]], [[Diana, New York|Diana]], [[Rossie, New York|Rossie]], [[Fine, New York|Fine]], [[Pitcairn, New York|Pitcairn]], [[Brewster, New York|Brewster]], [[New York (state)|New York]]<ref name="Dana"/> and [[California]] in the US.

==Uses==
Titanite is a source of [[titanium dioxide]], TiO<sub>2</sub>, used in [[pigment]]s.

As a gemstone, titanite is usually some shade of [[Chartreuse (color)|chartreuse]], but can be brown or black. Hue depends on iron (Fe) content, with low Fe content causing green and yellow colours, and high Fe content causing brown or black hues. Zoning is typical in titanite. It is prized for its exceptional [[dispersion (optics)|dispersive]] power (0.051, B to G interval) which exceeds that of [[diamond]].<ref>{{Cite web |title=Sphene (Titanite) Value, Price, and Jewelry Information |url=http://www.gemsociety.org/article/sphene-jewelry-and-gemstone-information/ |website=International Gem Society}}</ref> Jewelry use of titanite is limited, both because the stone is uncommon in gem quality and is relatively soft.

Titanite can also be used as a U-Pb geochronometer, specifically in metamorphic terranes.

==In popular culture==
Titanite is commonly mentioned in the Dark Souls video game series as a material used to upgrade weapons and various other items.

==Image gallery==
<gallery widths="133px" heights="130px">
File:Titanit.jpg|Specimen from the mineral collection of the [[Naturmuseum Senckenberg]] in Frankfurt am Main
File:Titanite-tt56a.jpg|Titanite crystal that is totally gemmy and transparent, with a light olive-green color, perched on matrix of calcite and epidote
File:Titanite-Adularia-Clinochlore-275128.jpg|Bright green, twinned crystal of titanite with adularia and minor clinochlore on matrix
File:Titanite-163984.jpg|Olive-green titanite spear point set in matrix from Pakistan
File:Titanite-37979.jpg|Green titanite crystal perched right at the top of a column of gray, chlorite-included crystals
File:Titanite-23006.jpg|Yellow-green titanite twinned crystal perched vertically on the matrix
</gallery>

==References==
{{Reflist}}

==External links==
{{Commons category|Titanite}}
* [http://www.gggems.com/madagascar_sphene.htm Madagascar Sphene Properties, Occurrences and Geological data]

{{Titanium minerals}}
{{Authority control}}

[[Category:Monoclinic minerals]]
[[Category:Minerals in space group 14]]
[[Category:Gemstones]]
[[Category:Radioactive gemstones]]
[[Category:Calcium minerals]]
[[Category:Titanium minerals]]
[[Category:Nesosilicates]]