Syngenite information

Syngenite
Syngenite
	Tapering crystal of syngenite (size: 4.4 × 1.3 × 0.6 cm)
General
Category	Sulfate mineral
Formula; (repeating unit)	K2Ca(SO4)2·H2O
IMA symbol	Sgn
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

Syngenite is an uncommon potassium calcium sulfate mineral with formula K₂Ca(SO₄)₂·H₂O. It forms as prismatic monoclinic crystals and as encrustations.

^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
^ Handbook of Mineralogy
^ Syngenite on Mindat.org
^ Syngenite data on Webmineral
^ Atkins M, Glasser FP, Moron IP, Jack JJ, 1993. Thermodynamic modelling of blenede cemnts at elevated temperature (50–90 °C).

[1] Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.

[HBM-2] Handbook of Mineralogy

[Mindat-3] Syngenite on Mindat.org

[Webmin-4] Syngenite data on Webmineral

[Atkins-5] Atkins M, Glasser FP, Moron IP, Jack JJ, 1993. Thermodynamic modelling of blenede cemnts at elevated temperature (50–90 °C).

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