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From Wikipedia, the free encyclopedia
Syngenite is an uncommon potassium calcium sulfate mineral with formula K2Ca(SO4)2·H2O. It forms as prismatic monoclinic crystals and as encrustations.
Syngenite | |
---|---|
General | |
Category | Sulfate mineral |
Formula (repeating unit) | K2Ca(SO4)2·H2O |
IMA symbol | Sgn[1] |
Strunz classification | 7.CD.35 |
Dana classification | 29.3.1.1 |
Crystal system | Monoclinic |
Crystal class | Prismatic (2/m) (same H-M symbol) |
Space group | P21/m |
Unit cell | a = 9.77 Å, b = 7.14 Å c = 6.25 Å; β = 104.01°; Z = 2 |
Identification | |
Color | Colorless, milky white to faintly yellow due to inclusions |
Crystal habit | Tabular to prismatic crystals, lamellar aggregates and crystalline crusts |
Twinning | Common on {101} contact twins |
Cleavage | Perfect on {110} and {100}, distinct on {010} |
Fracture | Conchoidal |
Tenacity | Brittle |
Mohs scale hardness | 2.5 |
Luster | Vitreous |
Streak | White |
Diaphaneity | Transparent to translucent |
Specific gravity | 2.579–2.603 |
Optical properties | Biaxial (−), colorless (transmitted light) |
Refractive index | nα = 1.501 nβ = 1.517 nγ = 1.518 |
Birefringence | δ = 0.017 |
2V angle | Measured: 28° |
Solubility | Partially dissolves in water |
References | [2][3][4][5] |
It was first described in 1872 for an occurrence as druse on halite in the Kalusa Salt deposit, Ivanovo-Frankovsk Oblast', Ukraine.[3] The name is from Greek 'συγγενής' (related) due to its chemical similarity to polyhalite.[4][3]
It occurs in marine evaporite deposits as a diagenetic phase. It also forms as a volcanic sublimate, as vein fillings in geothermal fields and in caves where it is derived from bat guano. It occurs in association with halite and arcanite in salt deposits; and with biphosphammite, aphthitalite, monetite, whitlockite, uricite, brushite and gypsum in cave environments.[2]
It is also found in hardened cement which has relatively higher amount of potassium. [5]
Syngenite can be artificially produced by the action of a potassium sulfate solution on gypsum.[6]
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