Keyite

{{Short description|Mineral}}

{{Infobox mineral

| name = Keyite

| category = Arsenate minerals

| image = Keyite-91228.jpg

| imagesize = 260px

| caption = Keyite on adamite (greenish)

| formula = {{chem2|auto=1|Cu3(2+)Zn4Cd2(AsO4)6 * 2H2O}}

| IMAsymbol = Key{{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}}

| molweight = 1,520.19 g/mol

| strunz = 8.CA.50

| system = Monoclinic

| class = Prismatic (2/m)
(same H-M symbol)

| symmetry = I2/a

| unit cell = a = 11.654(3) Å
b = 12.780(5) Å
c = 6.840(3) Å
β = 99.11°; Z = 2

| color = azure/ blue

| habit = prismatic, tabular

| twinning =

| cleavage = good (001) cleavage

| fracture =

| tenacity =

| mohs = 3.5 - 4

| luster =

| refractive = nα = 1.800, nβ, and nγ = 1.870

| opticalprop = biaxial

| birefringence = 0.070

| pleochroism = x: pale blue, y: greenish blue, z: deep blue

| streak = light blue

| gravity =

| density = 5.106g/cm³

| melt =

| fusibility =

| diagnostic =

| solubility =

| diaphaneity = translucent

| other =

| references = Fleischer, M., Cabri, L.J., and Pabst, A. (1977) New Mineral Names. American Mineralogist, 62, 1259.

{{cite journal |last1=Cooper |first1=M.A. |last2=Hawthorne |first2=F.C. |year=1996 |title=The crystal structure of keyite, Cu₃²⁺Zn₄Cd₂(AsO₄)₆(H₂O)₂, an oxysalt mineral with essential cadmium |journal=Canadian Mineralogist |volume=34 |pages=623–630 |url=https://pubs.geoscienceworld.org/canmin/article-abstract/34/3/623/12770/The-crystal-structure-of-keyite-Cu-super-2-3-Zn-Cu |access-date=22 May 2022}}

}}

Keyite is a mineral with the chemical formula {{chem2|auto=1|Cu3(2+)Zn4Cd2(AsO4)6 * 2H2O}}. The name comes from Charles Locke Key (born 1935), an American mineral dealer who furnished its first specimens.

Keyite is monoclinic-prismatic, meaning its crystal form has three unequal axes, two of which have 90° angles between them and one with an angle less than 90°.

Keyite belongs to the biaxial optical class, meaning it has more than one axis of anisotropy (optic axis), in which light travels with zero birefringence, and three indices of refraction, nα = 1.800, nβ, and nγ = 1.870.{{mindat|name=Keyite|id=2191|accessdate=22 May 2022}}{{WebMineral|name=Keyite|url=http://webmineral.com/data/Keyite.shtml |accessdate=22 May 2022}} Being a very rare cadmium copper arsenate, keyite is only found in Tsumeb, Namibia in the Tsumeb mine, a world-famous copper mine known for its abundance of rare and unusual minerals.