Vesuvianite (also known as Idocrase)
Current inventory:  1 gem
 

  
Vesuvianite is named after its locality of discovery on Mt. Vesuvius, Campania, Italy. The name Idocrase is from the Greek words idos and krasis, meaning mixed appearance due to its varied crystal shapes. Vesuvianite is the IMA approved name, Idocrase is not.

Discovered in 1795; IMA status: Valid (pre-IMA; Grandfathered)

Chemistry

Chemical Formula:

Ca₁₉Al₄Fe(Al,Mg,Fe)₈Si₁₈O₇

Calcium Aluminum Iron Silicate

Molecular Weight:

1,422.09 gm

Composition:

Calcium

28.18 %

Ca

39.43 %

CaO

Magnesium

3.42 %

Mg

5.67 %

MgO

Aluminum

7.59 %

Al

14.34 %

Al₂O₃

Silicon

17.77 %

Si

38.03 %

SiO₂

Hydrogen

0.28 %

H

2.53 %

H₂O

Oxygen

42.75 %

O

100.00 %

100.00 %

= TOTAL OXIDE

Classification

Mineral Classification:

Silicates (Germanates)

Strunz 8th Ed. ID:

8/C.26-10

Nickel-Strunz 10th Ed. ID:

9.BG.35

9 : SILICATES (Germanates)
B : Sorosilicates
G : Sorosilicates with mixed SiO₄ and Si₂O₇ groups; cations in octahedral [6] and greater coordination

Related to:

Vesuvianite Group. Hydroxyl analogue of Fluorvesuvianite.

Members of Group:

Vesuvianite Group: Fluorvesuvianite, Manganvesuvianite, Vesuvianite, Wiluite

Varieties:

Beryllian Vesuvianite, Californite, Cerian Vesuvianite, Chrome-Vesuvianite, Cyprine, Frugardite, High-Hydrated Si-Deficient Vesuvianite, Manganoan Vesuvianite, Xanthite

Synonyms:

Genevite, Idocrase, Jefreinoffite, Jevreinovite, Pyramidal Garnet, Vesuviana, Volcanic Chrysotile

Crystal Data

Crystallography:

Tetragonal - Dipyramidal

Crystal Habit:

Crystals commonly as short pyramidal to long prismatic crystals, to 15 cm, morphologically complex, with up to 30 forms reported on one crystal; columnar, granular, massive. Californite is found in massive form, not as crystals.

Twinning:

Twinned domains observed at a very fine scale.

Physical Properties

Cleavage:

Indistinct on {110}, {100} and {001]

Fracture:

Irregular/Uneven, Sub-conchoidal

Tenacity:

Brittle

Moh's Hardness:

6.0 - 7.0

Density:

3.32 - 3.47 (g/cm³)

Luminescence:

None

Radioactivity:

Not Radioactive

Optical Properties

Color:

Green, Brown, Colorless to White, Blue (Cyprine), Violet, Bluish green, Pink, Red, Black, commonly zoned; in transmitted light, Colorless to light Yellow, Green, Brown

Transparency:

Transparent, Translucent

Luster:

Vitreous, Resinous

Refractive Index:

1.698 - 1.742  Uniaxial ( -/+ ) and Biaxial

Birefringence:

0.0040 - 0.0060

Dispersion:

Strong; 0.019 - 0.025

Pleochroism:

Weak; O = colorless to yellowish, E = yellowish, greenish, brownish

Occurances

Geological Setting:

In skarns formed during contact or regional metamorphism of limestones; in garnetized gabbros, mafic and ultramafic rocks, and serpentinites; uncommon in alkalic igneous rocks.

Common Associations:

Grossular, Diopside, Wollastonite, Epidote, Scapolite, Spinel, Calcite

Common Impurities:

Fe, Be, B, F, Cu, Li, Na, K, Mn, Ti, Cr, Zn, H₂O

Type Locality:

Monte Somma, Somma-Vesuvius Complex, Naples Province, Campania, Italy

Year Discovered:

1795

View mineral photos:

Vesuvianite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Vesuvianite (also known as Idocrase) is found in colors ranging from green to brown and also a blue variety called Cyprine. The complexities of its chemistry leads to the wide range of colors and properties. The green variety is similar in color to Peridot gems. Cyprine, the blue variety of Vesuvianite, is colored by the addition of copper to its chemistry and is also refered to as Cupreous Idocrase or Cupreous Vesuvianite.

There are many sources of Vesuvianite such as Asbestos, Quebec, Canada; California, Colorado and the New England region of USA; Mt. Vesuvius, Italy; Ural Mountains, Russia, Switzerland, Tanzania and Kenya. However, there are only a few sources of gem quality crystals. A small amount of gemmy material has come from Asbestos, Quebec, Canada. Recent finds in Tanzania and Kenya have brought some very nicely colored gems to the market. One source of material is from California, USA and has been nick-named Californite or California Jade. This bright green opaque to translucent material comes from near Happy Jack mine, Siskiyou County and near Pulga, Butte County, California.
 

  
Vesuvianite gems for sale: