Sylvite
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Sylvite was named in 1832 by French mineralogist and geologist François Sulpice Beudant (1787-1850) after François Sylvius de le Boe (1614-1672), a physician and chemist of Leyden, Netherlands.

Discovered in 1832; IMA status: Valid (pre-IMA; Grandfathered)

Chemistry

Chemical Formula:

KCl

Potassium Chloride

Molecular Weight:

74.55 gm

Composition:

Potassium

52.45 %

K

63.18 %

K₂O

Chlorine

47.55 %

Cl

47.55 %

Cl

—

 —  %

Cl

-O=Cl₂

100.00 %

100.00 %

= TOTAL OXIDE

Classification

Mineral Classification:

Halides

Strunz 8th Ed. ID:

3/A.02-40

Nickel-Strunz 10th Ed. ID:

3.AA.20

3 : HALIDES
A : Simple halides, without H₂O
A : M:X = 1:1, 2:3, 3:5, etc.

Related to:

Halite Group.

Members of Group:

Halite Group.

Varieties:

None

Synonyms:

Chloride of Potassium, Hoevelite, Hövelite, Leopoldite, Muriate of Potash, Potassium Chloride, Sal digestivus sylvii, Schätzelite, Silvinite, Silvite, Sylvin, Sylvine, Sylvyne

Crystal Data

Crystallography:

Isometric - Hexoctahedral 

Crystal Habit:

As cubes, cubo-octahedra, and octahedra, to 15 cm; may be columnar, in crusts, coarse granular to compact, massive. 

Twinning:

On {111} (artificial crystals only).

Physical Properties

Cleavage:

Perfect on {001}

Fracture:

Irregular/Uneven

Tenacity:

Brittle

Moh's Hardness:

1.5 - 2.0

Density:

1.993 (g/cm³)

Luminescence:

None

Radioactivity:

Mild; GRapi = 730.82 (Gamma Ray American Petroleum Institute Units)

Other:

Melts at 790°. Highly diathermanous (having the property of transmitting radiant heat; diathermal).

Optical Properties

Color:

Colorless to white, pale gray, seldom pale blue or violet; yellowish red to red when included with hematite; colorless in transmitted light.

Transparency:

Transparent, translucent

Luster:

Vitreous

Refractive Index:

1.4903

Birefringence:

0.000 (Isotropic)

Dispersion:

n/a

Pleochroism:

Visible. Distinct pleochroism observed in colored crystals with weak anomalous birefringence (especially noted in mechanically deformed crystals).

Anisotropism:

Anomalously weakly anisotropic when strained.

Occurances

Geological Setting:

In sedimentary basins, forming thick bedded deposits with halite; as a sublimate in volcanic fumaroles; in nitrate beds and cave deposits; a product of burning coal; may be included in other minerals as a product of intermediate-grade metamorphism.

Common Associations:

Halite, Kieserite, Kainite, Carnallite, Polyhalite, Gypsum, Anhydrite

Common Impurities:

Br, CO₂=C, O

Type Locality:

Mt. Vesuvius, Somma-Vesuvius Complex, Naples Province, Campania, Italy

Year Discovered:

1832

View mineral photos:

Sylvite Mineral Photos and Locations

Unusual Gem Categories

Radioactive Gems, Water Soluble Gems

More Information

Mindat.org
Webmineral.com

Sylvite

Sylvite, also called sylvine, is a major source of potassium or potash used in fertilizer products. So great is the need for potassium that sylvite deposits are considered very valuable economically. As a mineral specimen sylvite does not get much attention. The crystals can be well formed and are often reddish due to inclusions of hematite. However, sylvite is very soluble in water and specimens need to be stored in closed containers because even the moisture in the air can degrade its appearance. Never clean a sylvite specimen with water!

Sylvite is closely related to the more common Halite, NaCl, and they share so many properties that identification is sometimes difficult. Sylvite commonly has octahedral faces truncating the corners of the cubic crystals. So does halite, but this characteristic is much more prevalent in sylvite than in halite. Better tests include a taste test in which halite, salt, will taste salty and sylvite tastes bitter. This test is good if you need to distinguish one or two specimens, but what if you are testing hundreds of feet of core samples for beds of sylvite verses halite. A good test in those cases is the knife test in which a knife blade when scratched across the surface of the sample will produce a powder in halite and not in sylvite.

There is a low-sodium version of table salt (light salt) which is half halite and half sylvite. Naturally, it has half the sodium content of ordinary table salt, since that sodium has been replaced with potassium. It is a perfectly acceptable substitute for many people, while others consider it bitter.

Sylvite is potassium chloride (KCl) in natural mineral form. It forms crystals in the isometric system very similar to normal rock salt, Halite (NaCl).

is mildly radioactive due to its Potassium (K) content and is water soluble. Sylvite is one of the last evaporite minerals to precipitate out of solution. As such, it is only found in very dry saline areas. 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 named in 1832 by French mineralogist and geologist François Sulpice Beudant (1787-1850) after François Sylvius de le Boe (1614-1672), a physician and chemist of Leyden, Netherlands.

Sylvite distribution: On Vesuvius, Campania, Italy. At Hallein, Salzburg, Austria. In Germany, from Westeregeln and Stassfurt, 34 km south of Magdeburg, Saxony-Anhalt, and at Bernburg, Lower Saxony. At Aislaby, near Whitby, Yorkshire, England. From Kalusz, Ukraine. In the Verkhnekamsk sylvite deposit, Solikamsk-Berezniki region, Ural Mountains, Russia. In the USA, in the Permian salt basin of southeastern New Mexico, in the Carlsbad potash district, Eddy County with large crystals in the Potash Corporation of America mine, and adjacent parts of Texas. From the Smoky Hills, Peace River area, Alberta, Canada. Other minor localities are known.
 

  
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