Hanksite

Hanksite is a sulfate mineral, distinguished as one of only a handful that contain both carbonate and sulfate ions (a sulfate carbonate). It has the chemical formula Na22K(SO4)9(CO3)2Cl.

Hanksite
Hanksite crystal from Searles Lake
General
CategorySulfate minerals, sulfate carbonate
Formula
(repeating unit)
Na22K(SO4)9(CO3)2Cl
IMA symbolHks[1]
Strunz classification7.BD.30
Crystal systemHexagonal
Crystal classDipyramidal (6/m)
H–M symbol: (6/m)
Space groupP63/m
Unit cella = 10.465(21) Å
c = 21.191(43) Å; Z = 2
Identification
ColorColorless to pale yellow, may be grayish green due to clay inclusions
Crystal habitOccurs as short prismatic to tabular hexagonal crystals
CleavageGood on {0001}
FractureUneven
TenacityBrittle
Mohs scale hardness3–3.5
LusterVitreous to dull
StreakWhite
DiaphaneityTransparent to translucent
Specific gravity2.562
Optical propertiesUniaxial (−)
Refractive indexnω = 1.481, nε = 1.461
Birefringenceδ = 0.020
Ultraviolet fluorescencePale yellow under LW UV
SolubilityReadily soluble in water
References[2][3][4]

Occurrence

It was first described in 1888 for an occurrence in Searles Lake, California, and named for American geologist Henry Garber Hanks.[3][4] Hanksite is normally found in crystal form as evaporite deposits. Hanksite crystals are large but not complex in structure. It is often found in Searles Lake, Soda Lake, Mono Lake, and in Death Valley. At its deposits in San Bernardino County, California hanksite is commonly found beneath the surface embedded in mud or in drill cores (Palache et al., 1960). It is associated with halite, borax, trona, and aphthitalite at the Searles Lake locality.[2] It is also associated with borax mining in the Soda Lake area.

Physical characteristics

Hanksite can be colorless, white, gray, green, or yellow, and is transparent or translucent. The mineral's hardness is approximately 3 to 3.5. The specific gravity is approximately 2.5 (slightly below average). It is salty to the taste and sometimes glows pale yellow in ultraviolet light. Typical growth habits are hexagonal prisms or tabular with pyramidal terminations. The streak of Hanksite is white. It can contain inclusions of clay that the crystal formed around while developing.

Similar minerals

References

Bibliography

  • Palache, P.; Berman H.; Frondel, C. (1960). "Dana's System of Mineralogy, Volume II: Halides, Nitrates, Borates, Carbonates, Sulfates, Phosphates, Arsenates, Tungstates, Molybdates, Etc. (Seventh Edition)" John Wiley and Sons, Inc., New York, pp. 628-629.
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