Vesuvianite

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Vesuvianite
Vesuvianite Asbestos.jpg
Vesuvianite from the Jeffrey Mine in Asbestos, Quebec
General
Category Sorosilicate
Formula
(repeating unit)
Ca10(Mg, Fe)2Al4(SiO4)5(Si2O7)2(OH,F)4
Strunz classification 09.BG.35
Crystal symmetry Tetragonal 4/m 2/m 2/m
Unit cell a = 15.52 Å, c = 11.82 Å; Z = 2
Identification
Color Yellow, green, brown; colorless to white, blue, violet, bluish green, pink, red, black, commonly zoned
Crystal habit Short pyramidal to long prismatic crystals common, massive to columnar
Crystal system Tetragonal
Twinning Fine twin domains observed
Cleavage Poor on {110} and {100} very poor on {001}
Fracture Sub conchoidal to irregular
Mohs scale hardness 6 - 7
Luster Vitreous to resinous
Streak White
Diaphaneity Subtransparent to Translucent
Specific gravity 3.32 - 3.43
Optical properties Uniaxial (-)
Refractive index nω = 1.703 - 1.752 nε = 1.700 - 1.746
Birefringence 0.004-0.006
Pleochroism slight in colored varieties
Solubility Vesuvianite is virtually insolouble in acids
Other characteristics striated lengthwise
References [1][2]

Vesuvianite, also known as idocrase, is a green, brown, yellow, or blue silicate mineral. Vesuvianite occurs as tetragonal crystals in skarn deposits and limestones that have been subjected to contact metamorphism.[2] It was first discovered within included blocks or adjacent to lavas on Mount Vesuvius, hence its name. Attractive-looking crystals are sometimes cut as gemstones. Localities which have yielded fine crystallized specimens include Mount Vesuvius and the Ala Valley near Turin, Piedmont.

The specific gravity is 3.4 and the hardness 6 1/2. The name "vesuvianite" was given by A. G. Werner in 1795, because fine crystals of the mineral are found at Vesuvius; these are brown in colour and occur in the ejected limestone blocks of Monte Somma. Several other names have been applied to this species, one of which, "idocrase" by R. J. Haiiy (1796), is now in common use.

A sky bluish variety known as cyprine and as has been reported from Franklin, New Jersey and other locations; the blue is due to impurities of copper is a complex calcium aluminum sorosilicate. Californite is a name sometimes used for jade-like vesuvianite, also known as California-, American- or Vesuvianite-jade. Xanthite is a manganese rich variety. Wiluite is an optically positive variety from Wilui, Siberia. Idocrase is an older synonym sometimes used for gemstone-quality vesuvianite.

Tumbled vesuvianite pebble

References[edit]