Rainbow Garnet | Gemopedia

Also called "rainbow garnet," this gray to deep brown garnet displays phenomenal iridescence. The iridescence is caused by the way grossular and andradite garnet are mixed together in this single gem, forming a crystal structure that both scatters and traps light within the gem, creating a myriad of colors.
Colors
Greenish yellow to yellowish brown with iridescent rainbow colors

Rainbow Garnet Classification

Common Name

Rainbow Garnet

Species

Andradite

Variety

Iridescent Andradite

Colors

Greenish yellow to yellowish brown with iridescent rainbow colors

Alternate Names

Gemstone Groups

Garnet

Key Separations

OTL RI, SG magnification and appearance

Comments

Rare stones might show chatoyancy.

Rainbow Garnet Optical Properties

Transparency

Semitranslucent - Opaque

Refractive Index

1.888

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

Rainbow Garnet Chemistry & Crystallography

Chemical Name

calcium iron silicate

Chemical Formula

Ca3Fe2(SiO4)3

Synthesis

Crystal System

Cubic

Classification

Silicate

Nature

Natural

Crystallinity

Crystalline

Comments

Rainbow Garnet Characteristic Physical Properties

Hardness

6.5-7

Streak

White

Specific Gravity

3.81-3.87 Typical:3.84

Toughness

Varies

Inclusions

Iridescent andradite garnet is type II clarity stone. Iridescence is caused by twinning planes and occurs in parallel angled bands or patchy areas.

Luster

SubAdamantine

Stability

Fracture

Conchoidal, Uneven

Cleavage

None

Comments

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