Hydrogrossular Garnet | Gemopedia

Hydrogrossular garnet is typically translucent to opaque and is usually available as cabochons, but on rare occasion may be found as transparent, faceted gemstones. Generally seen as green to blue-green, pink, white, and gray, this gemstone may contain small dark gray to black inclusions and may look similar to jade if opaque. Hydrogrossular is a variety of grossular garnet where hydroxide partially replaces silica.
Colors
Green To Bluish Green, Pink, Brownish Pink, Rose Red, White, Gray

Hydrogrossular Garnet Classification

Common Name

Hydrogrossular Garnet

Species

Hydrogrossular

Variety

Colors

Green To Bluish Green, Pink, Brownish Pink, Rose Red, White, Gray

Alternate Names

Gemstone Groups

Garnet

Key Separations

RI, spectrum, appearance and maybe SG. If the stone is mixed with idocrase a clear identification is not possible.

Comments

Misnomers: African jade or Transvaal jade, garnet jade.

Hydrogrossular Garnet Optical Properties

Transparency

Translucent - Opaque

Refractive Index

1.72-1.72
Tolerance:(+0.010/-0.050)

Birefringence

Optic Character

NA

Optic Sign

NA

Polariscope Reaction

Aggregate (AGG)

Fluorescence

SWUV: Inert
LWUV: Inert

CCF Reaction

Green: possibly pinkish

Pleochroism

None

Dispersion

Comments

Hydrogrossular Garnet Chemistry & Crystallography

Chemical Name

calcium aluminum silicate with water or hydroxal

Chemical Formula

Ca3Al2(SiO4)3-x(OH)4x with (OH) partly replacing (SiO4)

Synthesis

Crystal System

Cubic

Classification

Silicate

Nature

Natural

Crystallinity

Aggregate

Comments

Hydrogrossular Garnet Characteristic Physical Properties

Hardness

7

Streak

Specific Gravity

3.15-3.55 Range:0.08/-0.32 Typical:3.47

Toughness

Good

Inclusions

Might have black magnetite inclusions that resemble pepper.

Luster

Vitreous

Stability

Good

Fracture

Uneven, Granular, Splintery

Cleavage

None

Comments

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