Garnet

Broadly speaking, you’ve got your reddish garnets and your non-reddish garnets. The reddish garnets are pyralspites, a compound abbreviation of pyropealmandine, and spessartine. The non-reddish garnets are ugrandites, a compound abbreviation of uvarovite, grossular, and andradite. (Note that the uvarovite and andradite links will take you to mindat.org; only pyrope, almandine, spessartine, and grossular are covered here.)

Because all garnets are isotropic and essentially identical in thin section, this is where you’ll find garnet images, GigaPans, and videos. If you’re looking for the characteristics of specific garnets, please refer to their individual pages.

Physical Properties
Chemical formula All garnets have chemistries

A3B2Si3O12

For the chemistries of specific garnets, refer to
their individual pages.

Class Nesosilicate
Isolated tetrahedra
Crystal system Cubic
Habit Dodecahedral
Trapezohedral
Usually euhedral to subhedral
Color Red (pyrope)
Deep red (almandine)
Pink (spessartine)
Violet (spessartine)
Brown (grossular, andradite)
Yellow (grossular, andradite)
Green (grossular, andradite)
Emerald green (uvarovite only)
Occasionally black (pyrope only)
Hardness 6.5-7.5
Specific gravity 3.54-4.19
Cleavage None
Fracture Subconchoidal to conchoidal
Luster Resinous
Transparency Transparent to translucent
Streak White
Optical Properties
PPL High relief
Colorless or pale
May look mottled grey
XPL Isotropic
δ None
after Perkins, 337-340

Garnet in Hand Sample

Garnet in garnet schist

Garnet in uncut garnet schist

Garnet in Archean-aged basement rock from Montana

Glorious almandine porphyroblasts in a schist from Alaska

Small garnets in the Castner Marble of West Texas

Small garnet hand sample

Garnet-bearing anorthosite

Garnet in the Maidens gneiss of Virginia’s Goochland Terrane (the thin section in the GigaPans below is Maidens gneiss)

Garnet in blueschist after eclogite (blueschist! after! eclogite! oh man!)

Garnet in Thin Section

Thin Section GigaPans

Garnet mica schist in plane polars

Garnet mica schist in crossed polars

Garnet in the Maidens Gneiss of Virginia’s Goochland Terrane, plane polars

Garnet in the Maidens Gneiss of Virginia’s Goochland Terrane, crossed polars

Sillimanite-garnet gneiss, plane polars

Sillimanite-garnet gneiss, crossed polars

Subhedral garnet, plane polars

Subhedral garnet, crossed polars

Anhedral garnet, plane polars

Anhedral garnet, crossed polars

Further Reading

Garnet at webmineral.com

Garnet at mindat.org