Changoite

Changoite is a rare zinc sulfate mineral with the formula Na₂Zn(SO₄)₂·4H₂O.[4][2] Chagoite was discovered in the San Francisco Mine near Sierra Gorda, Antofagasta, Chile.[3] The mineral is a zinc-analogue of blödite, cobaltoblödite, manganoblödite and nickelblödite - other representatives of the blödite group.[4] In terms of chemistry changoite is somewhat similar to gordaite.[5] The mineral's name comes from the early inhabitants of Chile - Changos.[3]

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
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	[1][2][3][4]

Traces of magnesium and calcium in changoite are negligible.[3]

Minerals associating with changoite are gypsum, zinc-bearing paratacamite, and thénardite.[2]

References

1. Mineralienatlas
2. Schlüter, J., Klaska, K.-H., and Gebhard, G., 1999. Changoite, Na₂Zn(SO₄)₂·4H₂O, the zinc analogue of blödite, a new mineral from Sierra Gorda, Antofagasta, Chile. Neues Jahrbuch für Mineralogie - Monatshefte 3(3), 97-103.
3. "Chagoite- Handbook of Mineralogy" (PDF). Handbookofmineralogy.org. Retrieved 2016-03-11.
4. "Changoite: Changoite mineral information and data". Mindat.org. Retrieved 2016-03-11.
5. "Gordaite: Gordaite mineral information and data". Mindat.org. Retrieved 2016-03-11.