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Mineral Silvina GDFL105.jpg
CategoryHalide mineral
(repeating unit)
Strunz classification3.AA.20
Crystal systemIsometric
Crystal classHexoctahedral (m3m)
H-M symbol: (4/m 3 2/m)
Space groupFm3m
Unit cella = 6.2931 Å; Z = 4
Formula mass74.55 g/mol
ColorColorless to white, pale gray, pale blue; may be yellowish red to red due to hematite inclusions
Crystal habitAs cubes and octahedra; columnar, in crusts, coarse granular, massive
CleavagePerfect on [100], [010], [001]
TenacityBrittle to ductile
Mohs scale hardness2
DiaphaneityTransparent to translucent
Specific gravity1.993
Optical propertiesIsotropic
Refractive index1.4903
PleochroismVisible in colored crystals
Ultraviolet fluorescenceNone
SolubilitySoluble in water
Other characteristicssalty to bitter taste

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.[4] 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.[5] Sylvite has a salty taste with a distinct bitterness.

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

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, Canada were formed by the evaporation of a Devonian seaway. Sylvite is the official mineral of Saskatchewan.

Sylvite was first described in 1832 at Mt. Vesuvius near Napoli in Italy and named for the Dutch chemist, François Sylvius de le Boe (1614–1672).[1]

Sylvite, along with quartz, fluorite and halite, is used for spectroscopic prisms and lenses.[6]

See also[edit]


  1. ^ a b Sylvite: Sylvite mineral information and data
  2. ^ Sylvite Mineral Data
  3. ^ Handbook of Mineralogy
  4. ^ Klein, Cornelis and Cornelius S. Hurlbut, Jr. 1993. Manual of Mineralogy after J.D. Dana, 21st edition. New York: John Wiley & Sons, Inc.
  5. ^ Deer, W.A., R.A. Howie, and J. Zussman. 1992. An Introduction to the Rock-Forming Minerals 2nd ed. New York: Prentice Hall.
  6. ^ "Motz, Lloyd. "Spectroscopy." Microsoft® Encarta® 2009". S (2009): 1841. Cite journal requires |journal= (help)

External links[edit]

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