Apachite

Apachite is a copper silicate mineral with a general formula of Cu9Si10O29·11H2O.[4] The name is associated with the Apache tribe residents of the area near the Christmas copper mine in the Dripping Spring Mountains of Gila County, Arizona, the location where apachite was first described in 1980.[5]

Apachite
General
CategorySilicate mineral
Formula
(repeating unit)		Cu9Si10O29·11(H2O)
IMA symbolApa[1]
Strunz classification9.HE.10
Crystal systemMonoclinic
Unknown space group
Unit cella = 12.89, b = 6.055
c = 19.11 [Å], β = 90.42°
V = 1,490.24 Å3; Z = 2
Identification
Formula mass1514.92 g/mol
Colorlight blue
Crystal habitspherical, rounded aggregates
Mohs scale hardness2
Lusternonmetallic, silky
Streaklight blue
Diaphaneitytranslucent
Specific gravity3.37
Optical propertiesbiaxial negative
Refractive indexnα=1.610, nβ=1.650, nγ=1.650
Birefringenceδ = 0.040
2V angleSmall
References[2][3]

Apachite has monoclinic crystal symmetry, displaying 3 axes of unequal length with two of the axes perpendicular to each other as well as one angle oriented less than 90°.[3] The mineral has a maximum birefringence value of δ = 0.040 which describes the difference between the highest and lowest index of refraction for the mineral. Apachite is an anisotropic mineral, so the velocity of light varies for this mineral.

It occurs in retrograde metamorphic environment as fractures cutting garnet diopside skarn. It occurs associated with kinoite, gilalite, stringhamite, junitoite, clinohedrite, xonotlite, apophyllite, calcite and tobermorite.[3]

References
  1. Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. Webmineral data
  3. Handbook of Mineralogy
  4. American Geological Institute. University of Texas Libraries Archived 2010-06-10 at the Wayback Machine. "Glossary of Geology." September 8, 2010
  5. Mindat.org


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