Sylvite

Sylvite, or sylvine, is potassium chloride (KCl) in natural mineral form. It forms crystals in the isometric system very similar to normal rock salt, halite (NaCl). The two are, in fact, isomorphous.^[5] Sylvite is colorless to white with shades of yellow and red due to inclusions. It has a Mohs hardness of 2.5 and a specific gravity of 1.99. It has a refractive index of 1.4903.^[6] Sylvite has a salty taste with a distinct bitterness.

Sylvite
General
Category	Halide mineral
Formula (repeating unit)	KCl
IMA symbol	Syl[1]
Strunz classification	3.AA.20
Crystal system	Isometric
Crystal class	Hexoctahedral (m3m) H-M symbol: (4/m 3 2/m)
Space group	Fm3m
Unit cell	a = 6.2931 Å; Z = 4
Identification
Formula mass	74.55 g/mol
Color	Colorless to white, pale gray, pale blue; may be yellowish red to red due to hematite inclusions
Crystal habit	As cubes and octahedra; columnar, in crusts, coarse granular, massive
Cleavage	Perfect on [100], [010], [001]
Fracture	Uneven
Tenacity	Brittle to ductile
Mohs scale hardness	2
Luster	Vitreous
Streak	White
Diaphaneity	Transparent to translucent
Specific gravity	1.993
Optical properties	Isotropic
Refractive index	1.4903
Pleochroism	Visible in colored crystals
Ultraviolet fluorescence	None
Solubility	Soluble in water
Other characteristics	Salty to bitter taste
References	[2][3][4]

Sylvite is one of the last evaporite minerals to precipitate out of solution. As such, it is found only in very dry saline areas. Its principal use is as a potassium fertilizer.

Sylvite

Sylvite from Germany

Sylvite is found in many evaporite deposits worldwide. Massive bedded deposits occur in New Mexico and western Texas, and in Utah in the US, but the largest world source is in Saskatchewan, Canada. The vast deposits in Saskatchewan were formed by the evaporation of a Devonian seaway. Sylvite is the official mineral of Saskatchewan.

Sylvite was first described in 1832 at Mount Vesuvius near Napoli in Italy and named after historical KCl designations sal degistivum Sylvii and sal febrifugum Sylvii,^[7] which are named after the Dutch physician and chemist François Sylvius de le Boe (1614–1672).^[2]

Sylvite, along with quartz, fluorite and halite, is used for spectroscopic prisms and lenses.^[8]

See also

• Sylvinite – Sedimentary rock made of a mechanical mixture of sylvite and halite

References

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.
2. Sylvite: Sylvite mineral information and data
3. Sylvite Mineral Data
4. Handbook of Mineralogy
5. Klein, Cornelis and Cornelius S. Hurlbut, Jr. 1993. Manual of Mineralogy after J.D. Dana, 21st edition. New York: John Wiley & Sons, Inc.
6. Deer, W.A., R.A. Howie, and J. Zussman. 1992. An Introduction to the Rock-Forming Minerals 2nd ed. New York: Prentice Hall.
7. Watts, Henry (1883). A Dictionary of Chemistry and the Allied Branches of Other Sciences. Longmans, Green, and Company.
8. Motz, Lloyd. "Spectroscopy". Microsoft Encarta 2009. S (2009): 1841.

External links

• Mineral Resources of Saskatchewan

Chisholm, Hugh, ed. (1911). "Sylvite" . Encyclopædia Britannica (11th ed.). Cambridge University Press.