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Grossular

Crystal system · Isometric

Grossular is a silicate mineral prized by collectors for its exceptional color range, with known Chinese sources.

About Grossularextended article

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Crystal Structure
Ca₃Al₂(SiO₄)₃.
External databases provide CIF (Crystallographic Information File) downloads + interactive 3D viewers. AMCSD: American Mineralogist Crystal Structure Database (free, RRUFF-hosted). COD: open community-curated database.
Elemental Composition (by mass)
ElementMass %Visual
O Oxygen42.62%
Ca Calcium26.69%
Si Silicon18.71%
Al Aluminum11.98%
Computed from simplified end-member formula. Solid-solution series, water content, and trace substitutions cause real-world variation.
IMA Abbreviation (Whitney-Evans 2010)
Grs
→ Grossular
Garnet
Standard symbol from American Mineralogist (Whitney & Evans, 2010). Used in thin-section labeling, phase diagrams, and IMA-style species records.
Pronunciation
/ˈɡrɒsjələr/
↔ GROSS-yuh-lar
from gooseberry (Latin grossularia)
Luster
vitreous
Standard vitreous.
Notable localities (coordinates)
All localities and full GeoJSON available at /wp-json/mmb/v1/localities-geo
Diaphaneity (Transparency)
transparent-to-translucent
Including tsavorite (gem) and hessonite (transparent).
Type Locality
Wilui River, Sakha — Russia
Described 1808 by Werner
Magnetism
Category:
diamagnetic
Test result:
Very slightly repelled or null
Ca-Al garnet — no transition metal; pure grossular is diamagnetic.
Test with rare-earth magnet (N42 or N52 neodymium). Suspend specimen on thread for sensitive paramagnetic detection. Diamagnetic minerals are weakly repelled (visible only with strong magnets like bismuth).
Specific Gravity
3.42–3.72
g/cm³
medium
Ca-Al garnet; includes tsavorite, hessonite.
For comparison: water = 1.00, glass ≈ 2.5, quartz = 2.65, corundum ≈ 4.00, galena ≈ 7.50, gold ≈ 19.3.
Geological Setting
Environment:
metamorphic
Host rock:
skarn, rodingite
Companions:
Wollastonite · Epidote · Diopside
Forms in contact-metamorphic calc-silicate rocks.
Mohs 6.5–7
Vickers (~) 1400 HV
Knoop (~) 1100 HK
Geological setting
Skarn
Element composition by mass

Formula: Ca₃Al₂(SiO₄)₃ · molar mass: 450.44 g/mol

O 42.62%
Ca 26.69%
Si 18.71%
Al 11.98%

Computed from atomic weights (IUPAC 2021). Site-occupancy groups (Fe,Mn) split equally.

GroupGarnet Group
Related members: Almandine · Pyrope · Spessartine · Andradite · Uvarovite
Mohs Hardness 6.5–7

Grossular sits at 6.5–7 on the Mohs scale — harder than glass; scratches steel.

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Colors:
Streak
White
Crystal system
Isometric (Cubic)
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SilicatesSilicates (Nesosilicates)
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TL;DR · 1 min read
Grossular (Ca₃Al₂(SiO₄)₃) is the calcium-aluminum end-member of the garnet group and one of the most variably colored garnet species. Its name comes from Latin "grossularia" (gooseberry) for its original pale-green specimens.
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Grossular (Ca₃Al₂(SiO₄)₃) is the calcium-aluminum end-member of the garnet group and one of the most variably colored garnet species. Its name comes from Latin “grossularia” (gooseberry) for its original pale-green specimens. Famous gem varieties include tsavorite (vivid chrome-vanadium green from Tanzania/Kenya) and hessonite (cinnamon-orange iron-bearing from Sri Lanka and Italy). Grossular is a classic skarn species, formed at the contact between calcareous rocks and granitic intrusions.

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Other Members of the Garnet Group

石榴石族

Identification & care

Crystals commonly develop as dodecahedral, trapezohedron; combinations; granular. Its color range is broad, including colorless, white, pale green, rich green (tsavorite), orange (hessonite/cinnamon stone), yellow, pink (leuco-grossular), and brown. The luster is vitreous, resinous, the streak is white, and specimens range from transparent to translucent. The fracture is conchoidal, uneven, which is one of its key identifying features.

Collector context

How it forms

In terms of geology, Grossular forms in metamorphic skarns (contact metamorphism with calcareous rocks), serpentinites, crystalline limestone; alluvial gem gravels. It is commonly found in association with diopside, wollastonite, calcite, vesuvianite, tremolite, zoisite (for tsavorite).

Classic Chinese localities

Grossular is widely represented across Chinese provinces, including Fujian, Gansu, Anhui, Guangdong.

Why collectors care

Grossular is a frequently-sought species in serious collections because its habit is recognizable, its color often strong, and its best examples unmistakable even at a distance. Chinese material has driven much of the recent visual shift in the species — sharper crystals, deeper colors, cleaner matrix.

What affects value

Value in Grossular is assessed, in typical order of weight, against: (1) locality provenance; (2) size relative to the species norm; (3) crystal form and termination sharpness; (4) color saturation and zoning; (5) transparency and internal clarity; (6) matrix quality and aesthetic balance; (7) condition (absence of damage, chips, or repair). Cleaning quality and verified locality documentation act as multipliers across the above.

Naming history

The name Grossular has a specific etymological and historical context — see Mindat's reference entry for provenance details. We have retained naming data at the record level; published prose is paraphrased from factual fields rather than copied from source.