Changoite
Changoite is a rare zinc sulfate mineral with the formula Na2Zn(SO4)2·4H2O. Chagoite was discovered in the San Francisco Mine near Sierra Gorda, Antofagasta, Chile. The mineral is a zinc-analogue of blödite, cobaltoblödite, manganoblödite and nickelblödite - other representatives of the blödite group. In terms of chemistry changoite is somewhat similar to gordaite. The mineral's name comes from the early inhabitants of Chile - Changos.
| Changoite | |
|---|---|
Yellowish crystals of changoite associated to hexagonal colorless caracolite in an aesthetic combination. | |
| General | |
| Category | Sulfate mineral |
| Formula (repeating unit) | Na2Zn(SO4)2·4H2O |
| IMA symbol | Cgo |
| Strunz classification | 7.CC.50 (10 ed) 6/C.18-25 (8 ed) |
| Crystal system | Monoclinic |
| Crystal class | Prismatic (2/m) (same H-M symbol) |
| Space group | P21/a |
| Unit cell | a = 11.08, b = 8.25, c = 5.53 [Å], β = 100.18° (approximated); Z = 2 |
| Identification | |
| Color | Colorless |
| Crystal habit | Anhedral crystals, in small veins |
| Mohs scale hardness | 2-3 |
| Luster | Vitreous |
| Streak | White |
| Diaphaneity | Transparent |
| Specific gravity | 2.50 (measured) |
| Optical properties | Biaxal (-) |
| Refractive index | nα=1.51, nβ=1.51, nγ=1.52 (approximated) |
| 2V angle | 83° (calculated) |
| References | |
Traces of magnesium and calcium in changoite are negligible.
Minerals associating with changoite are gypsum, zinc-bearing paratacamite, and thénardite.
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