Pale blue gordaite associated with deep green crystals of herbertsmithite from the San Francisco Mine, Caracoles, Antofagasta Region, Chile.
General
Category
Sulfate mineral
Formula (repeating unit)
NaZn4(SO4)(OH)6Cl·6H2O
IMA symbol
Gda[1]
Strunz classification
7.DF.50
Crystal system
Trigonal
Crystal class
Rhombohedral (3) (same H-M symbol)
Space group
P3
Unit cell
a = 8.413, c = 13.095 [Å]; Z = 2
Identification
Color
Colorless to white, pale green with copper substitution
Crystal habit
Thin tabular flakes or blades, in rosette aggregates
Cleavage
Perfect on {0001}
Tenacity
Flexible
Mohs scale hardness
2.5
Luster
Vitreous to pearly
Specific gravity
2.627
Optical properties
Uniaxial (-)
Refractive index
nω = 1.561 nε = 1.538
Birefringence
δ = 0.023
References
[2][3]
Gordaite is a sulfate mineral composed primarily of hydrous zinc sodium sulfate chloride hydroxide with formula: NaZn4(SO4)(OH)6Cl·6H2O. It was named for the discovery location in the Sierra Gorda district of Chile. Gordaite forms as tabular trigonal crystals.
Gordaite first appeared after a research dive in September 1984 from the Juan de Fuca Ridge of the northeastern side of the Pacific Ocean. Gordaite was also described from weathered slag deposits as a result of copper smelting in Hettstedt, Germany.[4] The mineral exhibits a hexagonal shape with clear or white (green if cuprian – Cu2+) crystals ranging from planar to broad habit and has a point group of 3. Gordaite commonly occurs near minerals such as sphalerite, boleite and gypsum. The most recent finding occurred in the San Francisco mine in Chile where copper-zinc sulfide deposits were found.
^Nasdala, L., Witzke, T., Ullrich, B. and Brett, R. (1998): Gordaite [Zn4Na(OH)6(SO4)Cl•6H2O]: second occurrence in the Juan de Fuca Ridge, and new data. American Mineralogist 83, pg. 1111-1116.
Gordaite is a sulfate mineral composed primarily of hydrous zinc sodium sulfate chloride hydroxide with formula: NaZn4(SO4)(OH)6Cl·6H2O. It was named for...
mineral information and data". Mindat.org. Retrieved 2016-03-11. "Gordaite: Gordaite mineral information and data". Mindat.org. Retrieved 2016-03-11. v...
Nasdala, Lutz; Witzke, Thomas; Ullrich, Bernd; Brett, Robin (1998-10-01). "Gordaite [Zn 4 Na(OH) 6 (SO 4 )Cl.6H 2 O]; second occurrence in the Juan de Fuca...