Vesuvianite

Vesuvianite
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

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. It was first discovered within included blocks or adjacent to lavas on Mount Vesuvius, hence its name.

A bluish variety known as cyprine has been reported from Franklin, New Jersey and other locations; the blue is due to impurities of copper. 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

• Deere, W. A. et al., 1962, Rock Forming Minerals: Vol. 1 Ortho- and Ring Silicates, pp. 113 – 120
• Webmineral data
• Vesuvianite at Franklin -Sterling
• Mindat - Cyprine var. w/ location data