{{short description|Rare silicate mineral}} {{Infobox mineral | name = Kochite | category = Sorosilicates <br/>Rosenbuschite group | boxwidth = | boxbgcolor = | image = | imagesize = | caption = | formula = {{chem2|(Na,Ca)3Ca2(Mn,Ca)ZrTi[(F,O)4(Si2O7)2]}} | IMAsymbol = Koh<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> | molweight = | system = Triclinic | class = Pinacoidal ({{overline|1}}) <br/><small>(same H-M symbol)</small> | symmetry = ''P''{{overline|1}} | unit cell = a = 10.03, b = 11.33 <br/>c = 7.202&nbsp;[Å]; α = 90.19° <br/>β = 100.33°, γ = 111.55°; Z&nbsp;=&nbsp;2 | color = Colorless to light brown | habit = Acicular to lath-shaped prismatic crystals | twinning = | cleavage = {100} perfect | fracture = Uneven | tenacity = Brittle | mohs = 5 | luster = Vitreous | refractive = n<sub>α</sub>=1.684, n<sub>β</sub>=1.695, n<sub>γ</sub>=1.718 | opticalprop = Biaxial (+) | birefringence = 0.0340 | pleochroism = weak, colorless to pale brownish-yellow | streak = White | gravity = 3.32 | density = | melt = | fusibility = | diagnostic = | solubility = | diaphaneity = Transparent | other = | references = <ref name=Mindat>[http://www.mindat.org/min-25598.html Mindat.org]</ref><ref>[http://www.webmineral.com/data/Kochite.shtml Webmineral data]</ref><ref>[http://www.mineralienatlas.de/lexikon/index.php/MineralData?mineral=Kochite Mineralien Atlas]</ref> }}

'''Kochite''' is a rare silicate mineral with chemical formula of {{chem2|(Na,Ca)3Ca2(Mn,Ca)ZrTi[(F,O)4(Si2O7)2]}}<ref name=Mindat/> or double that.<ref>{{cite journal|last1=Jambor|first1=J.L.|last2=Roberts|first2=A.C.|date=January 2004|title=New Mineral Names|url=https://pubs.geoscienceworld.org/msa/ammin/article-abstract/89/1/249/44086/New-Mineral-Names|journal=American Mineralogist|volume=89|issue=1|pages=249–253|url-access=subscription}}</ref> Kochite is a member of the rosenbuschite group.<ref name=Johnsen2>[http://rruff.geo.arizona.edu/doclib/cm/vol41/CM41_1203.pdf Christiansen, Claes C., Ole Johnsen and Emil Makovicky, ''Crystal Chemistry of the Rosenbuscite Group,'' The Canadian Mineralogist, Vol. 41, pp. 1203-1224 (2003)]</ref>

==Crystallography== Kochite is triclinic with angles intersecting at approximately α 90.192°, β 100.192°, γ 111.551°. This mineral belongs to the space group P{{overline|1}} and is centrosymmetric, i.e. contains a center of symmetry.<ref> Mandarino, J.A. (2004) Abstracts of New Mineral Descriptions. The Mineralogy Record, 35, 354-355 </ref>

It is an anisotropic mineral as the light entering the mineral is split into two rays that vibrate at 90° to each other.<ref name=Mindat/> It is biaxial, meaning it has two optic axes (lines of symmetry). In plane polarized light, this mineral is colorless to light brown and is pleochroic. As the stage of the microscope is turned from X to Z the color changes from colorless to a pale brownish-yellow.<ref name=Christiansen>Christiansen, C.C., Gault, R.A., Grice, and J.D., Johnsen, O. (2003) Kochite, a new member of the rosenbuschite group from the Werner Bjerge alkaline complex, East Greenland. European Journal of Mineralogy, 15, 551-554 ]</ref> Kochite is also a birefringent mineral, showing bright colors under crossed polarization. Its birefringence is .0340.<ref name=Christiansen/>

==Discovery and occurrence== Kochite is found in the alkaline igneous complex of East Greenland and is named after Danish geologist Lauge Koch (1892-1964), a geologist who overturned the previous conception of Greenland's landscapes. It is the titanium – manganese analog of rosenbuschite and occurs in nepheline syenite associated with nepheline, alkali feldspar, and låvenite in the Werner Bjerge alkaline complex along the eastern coast of Greenland.<ref name=Christiansen/>

==References== {{Reflist}}

Category:Sorosilicates Category:Triclinic minerals Category:Minerals in space group 2