Vesuvianite from the Jeffrey Mine in Asbestos, Quebec
Category Mineral
Chemical formula Ca10(Mg, Fe)2Al4(SiO4)5(Si2O7)2(OH,F)4
Crystal symmetry Tetragonal 4/m 2/m 2/m
Unit cell a = 15.52 Å, c = 11.82 Å; Z = 2
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.

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