Tuesday, July 21, 2009

Vesuvianite

Vesuvianite

Vesuvianite
General
CategoryMineral
Chemical formulaCa10(Mg, Fe)2Al4(SiO4)5(Si2O7)2(OH,F)4
Identification
Molar mass1,422.09 gm
ColorYellow, green, brown - rarely blue or red
Crystal habitMassive to columnar
Crystal systemTetragonal
CleavagePoor to very poor
FractureSub conchoidal
Mohs Scalehardness6.5
LusterVitreous to resinous
StreakWhite
DiaphaneitySubtransparent to Translucent
Specific gravity3.35 - 3.45
Optical propertiesUniaxial (-)
Refractive indexnω = 1.702 - 1.742 nε = 1.698 - 1.736
Birefringence0.0040-0.0060
Pleochroismslight in colored varieties
SolubilityVesuvianite is virtually insolouble in acids
Other characteristicsstriated 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.


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