Vesuvianite

Vesuvianite
General
Category	Mineral
Chemical formula	Ca10(Mg, Fe)2Al4(SiO4)5(Si2O7)2(OH,F)4
Identification
Molar mass	1,422.09 gm
Color	Yellow, green, brown - rarely blue or red
Crystal habit	Massive to columnar
Crystal system	Tetragonal
Cleavage	Poor to very poor
Fracture	Sub conchoidal
Mohs Scalehardness	6.5
Luster	Vitreous to resinous
Streak	White
Diaphaneity	Subtransparent to Translucent
Specific gravity	3.35 - 3.45
Optical properties	Uniaxial (-)
Refractive index	nω = 1.702 - 1.742 nε = 1.698 - 1.736
Birefringence	0.0040-0.0060
Pleochroism	slight in colored varieties
Solubility	Vesuvianite is virtually insolouble in acids
Other characteristics	striated lengthwise

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 forjade-like vesuvianite, also known as California-, American- or Vesuvianite-jade. Xanthite is amanganese rich variety. Wiluite is an optically positive variety from Wilui, Siberia. Idocrase is an older synonym sometimes used for gemstone-quality vesuvianite.