Vesuvianite

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. 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.[4]

Vesuvianite
Vesuvianite from the Jeffrey Mine in Asbestos, Quebec
General
CategorySorosilicate
Formula
(repeating unit)
Ca10(Mg, Fe)2Al4(SiO4)5(Si2O7)2(OH,F)4
Strunz classification9.BG.35
Crystal systemTetragonal
Crystal classDitetragonal dipyramidal (4/mmm)
H-M symbol: (4/m 2/m 2/m)
Space groupP4/nnc
Unit cella = 15.52 Å, c = 11.82 Å
Z = 2
Identification
ColorYellow, green, brown; colorless to white, blue, violet, bluish green, pink, red, black, commonly zoned
Crystal habitShort pyramidal to long prismatic crystals common, massive to columnar
TwinningFine twin domains observed
CleavagePoor on {110} and {100} very poor on {001}
FractureSub conchoidal to irregular
TenacityBrittle
Mohs scale hardness6–7
LusterVitreous to resinous
StreakWhite
DiaphaneitySubtransparent to translucent
Specific gravity3.32–3.43
Optical propertiesUniaxial (−)
Refractive indexnω = 1.703–1.752
nε = 1.700–1.746
Birefringence0.004–0.006
Pleochroismslight in colored varieties
SolubilityVesuvianite is virtually insolouble in acids
Other characteristicsstriated lengthwise
References[1][2][3]

The specific gravity is 3.4 and the Mohs hardness is 6 12. The name "vesuvianite" was given by Abraham 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 of Monte Somma. Several other names were applied to this species, one of which, "idocrase" by René Just Haüy in 1796, is now in common use.[4]

A sky bluish variety known as cyprine has been reported from Franklin, 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 for jade-like vesuvianite, also known as California jade, American jade 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.

References

  1. Mindat with location data
  2. Handbook of Mineralogy
  3. https://www.mineralienatlas.de/lexikon/index.php/MineralData?mineral=Vesuvianite Mineralienatlas
  4.  One or more of the preceding sentences incorporates text from a publication now in the public domain: Spencer, Leonard James (1911). "Vesuvianite". In Chisholm, Hugh (ed.). Encyclopædia Britannica. 27 (11th ed.). Cambridge University Press. p. 1063.

Additional sources

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