Idocrase | Gemopedia

Idocrase, also known as vesuvianite after its discovery at Mount Vesuvius, has crystals that are prismatic and glassy. It is usually green or chartreuse in color, but may be found in yellow to brown, yellow-green, red, black, blue or purple hues.
Alternate
Names
Vesuvianite, Californite, Xanthite, Cyprine
Colors
Yellow To Green, Yellowish Brown, Light Blue To Greenish Blue, Gray, White

Idocrase Classification

Common Name

Idocrase

Species

Vesuvianite

Variety

Colors

Yellow To Green, Yellowish Brown, Light Blue To Greenish Blue, Gray, White

Alternate Names

Vesuvianite, Californite, Xanthite, Cyprine

Gemstone Groups

Key Separations

RI, birefringence, optic character, spectrum, possible pleochroism

Comments

Jade-like variety of idocrase is often mixed with hydrogrossular garnet. Misnomers: California jade.

Idocrase Optical Properties

Transparency

Transparent - Opaque

Refractive Index

1.713-1.718
Tolerance:(+0.003/-0.013)

Birefringence

0.001-0.012

Optic Character

Uniaxial

Optic Sign

Positive or Negative

Polariscope Reaction

Doubly Refractive (DR)

Fluorescence

SWUV: inert
LWUV: inert

CCF Reaction

Pleochroism

Dichroic, unobservable or weak, varying shades of body color

Dispersion

Strength: weak fire Value: 0.019

Comments

Idocrase Chemistry & Crystallography

Chemical Name

calcium magnesium aluminum silicate

Chemical Formula

Ca10Mg2Al4(SiO4)5(Si2O7)2(OH)4

Synthesis

Crystal System

Tetragonal

Classification

Silicate

Nature

Natural

Crystallinity

Crystalline to Aggregate

Comments

Idocrase Characteristic Physical Properties

Hardness

6.5

Streak

White

Specific Gravity

3.25-3.5 Typical:3.4

Toughness

Varies

Inclusions

Luster

Vitreous

Stability

Fracture

Conchoidal, Granular, Uneven

Cleavage

Poor, in three directions

Comments

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