Andradite Garnet | Gemopedia

Andradite is a fairly abundant, although less-known, member of the ugrandite garnet species, which also includes uvarovite and grossularite. Andradite makes spectacular gems that display greater color dispersion than diamond.
Alternate
Names
Topazilite, Melanite, Demantoid
Colors
Yellow, Greenish Yellow, Brown, Black

Andradite Garnet Classification

Common Name

Andradite Garnet

Species

Andradite

Variety

Colors

Yellow, Greenish Yellow, Brown, Black

Alternate Names

Topazilite, Melanite, Demantoid

Gemstone Groups

Garnet

Key Separations

OTL RI, lack of doubling, spectra

Comments

Topazilite is the translucent to transparent variety that is yellow, yellow-green or yellow-brown in color. Melanite is the opaque black variety that is subadamantine to vitreous luster. Demantoid: green to yellowish green and brownish green variety.

Andradite Garnet Optical Properties

Transparency

Transparent - Opaque

Refractive Index

Over the Limit 1.888-1.94

Birefringence

Optic Character

NA

Optic Sign

NA

Polariscope Reaction

Singly Refractive (SR) With ADR

Fluorescence

SWUV: Inert
LWUV: Inert

CCF Reaction

Pleochroism

None

Dispersion

Strength: strong fire Value: 0.057

Comments

Andradite Garnet Chemistry & Crystallography

Chemical Name

calcium iron silicate

Chemical Formula

Ca3Fe2(SiO4)3

Synthesis

Crystal System

Cubic

Classification

Silicate

Nature

Natural

Crystallinity

Crystalline

Comments

Andradite Garnet Characteristic Physical Properties

Hardness

6.5-7

Streak

Specific Gravity

3.81-3.87 Typical:3.84

Toughness

Poor

Inclusions

Andradite garnet is a type II clarity stone. Due to low mohs hardness stones might show surface abrasions or scratches.

Luster

SubAdamantine

Stability

Good

Fracture

Conchoidal, Uneven

Cleavage

None

Comments

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