| Vesuvianite | |
|---|---|
 Vesuvianite from the Jeffrey Mine inAsbestos, Quebec | |
| General | |
| Category | Sorosilicate |
| Formula | Ca10(Mg, Fe)2Al4(SiO4)5(Si2O7)2(OH,F)4 |
| IMA symbol | Ves[1] |
| Strunz classification | 9.BG.35 |
| Crystal system | Tetragonal |
| Crystal class | Ditetragonal dipyramidal (4/mmm) H-M symbol: (4/m 2/m 2/m) |
| Space group | P4/nnc |
| Unit cell | a = 15.52 Å,c = 11.82 Å Z = 2 |
| Identification | |
| Color | Yellow, green, brown; colorless to white, brown-black, light green, emerald green, violet, blue-green to blue, pink, purple, red, black, commonly zoned |
| Crystal habit | Short pyramidal to long prismatic crystals common, massive to columnar |
| Twinning | Fine twin domains observed |
| Cleavage | Poor on {110} and {100} very poor on {001} |
| Fracture | Sub conchoidal to irregular |
| Tenacity | Brittle |
| 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 insoluble in acids |
| Other characteristics | striated lengthwise |
| References | [2][3][4] |
Vesuvianite, also known asidocrase, is a green, brown, yellow, or bluesilicate mineral. Vesuvianite occurs astetragonalcrystals inskarn deposits andlimestones that have been subjected to contactmetamorphism.[3] It was first discovered within included blocks or adjacent tolavas onMount 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.[5]
Thespecific gravity is 3.4 and theMohs hardness is6+1⁄2. The name "vesuvianite" was given byAbraham Gottlob Werner in 1795, because fine crystals of the mineral are found at Vesuvius; these are brown in color and occur in the ejected limestone blocks ofMonte Somma. Several other names were applied to this species, one of which, "idocrase" byRené Just Haüy in 1796, is now in common use.[5]
A sky bluish variety known ascyprine has been reported fromFranklin, New Jersey and other locations; the blue is due to impurities of copper in a complex calcium aluminum sorosilicate.Californite is a name sometimes used forjade-like vesuvianite, also known asCalifornia jade,American jade orVesuvianite jade.Xanthite is amanganese rich variety.Wiluite is an optically positive variety from Wilui,Siberia. Idocrase is an older synonym sometimes used forgemstone-quality vesuvianite. Also,Vessonite andVassolite are variant spellings commonly encountered in the gem trade.
One or more of the preceding sentences incorporates text from a publication now in thepublic domain: Spencer, Leonard James (1911). "Vesuvianite". InChisholm, Hugh (ed.).Encyclopædia Britannica. Vol. 27 (11th ed.). Cambridge University Press. p. 1063.