Mineral Information and Data:

Grossular
Ca3Al2(SiO4)3 [CNMNC approved formula]

Named in 1811 for the green color of gooseberries (Ribes grossularium) because the original specimens were this color.

IMA status : Approved Species 1960 ()
CLASSIFICATION 
Dana
(8th edition) :
51.04.03b.02  
  (51) Nesosilicate Insular SiO4 Groups Only
  (51.04) with cations in [6] and >[6] coordination
  (51.04.03b) Garnet group (Ugrandite series)
  
Nickel-Strunz
(10th edition) :
09.AD.25
  (09) Silicates
  (09.A) Nesosilicates (Isolated tetrahedron) structures
  (09.AD) Nesosilicates without additional anions; cations in [6] and/or greater coordination
  
Crystal system: Cubic System
Point group (H-M): m3m (or 4/m 3 2/m) — hexoctahedral
Unit cell: a = 11.85 วบ
Crystal Habit: Crystals dodecahedrons or trapezohedrons; massive, compact; granular; embedded grains
  
Color: Colorless, white, gray, yellow to green, brown, pink, red, black
Diaphaneity: Transparent to opaque
Luster: Vitreous to resinous
Hardness (Mohs): 6.5 to 7
Measured Density: 3.4 to 3.6 g/cm3
Cleavage: Parting on {110} rarely observed
Tenacity: Brittle
Fracture: Uneven to conchoidal
Streak: White
  
Geologic Setting: In contact and regionally metamorphosed calcareous rocks, or rocks which have undergone calcium metasomatism; in some schists and serpentinites.
Mineral Association: Calcite, dolomite, epidote, clinozoisite, wollastonite, scapolite, vesuvianite, diopside, tremolite, quartz
  
Synonyms/varieties: Grossularite, hessonite/essonite (orange to red var.), tsavorite/tsavolite (gree, Cr/V-rich var.)
Other Properties: Gemstone Rare.
Comments: Forms three series: with andradite; with hibschite and katoite; and with uvarovite

 

Grossular
Origin: Lowell, Orleans Co., Vermont
Sample size: Microscopic image
Photo and Owner: Lou Perloff

 

Grossular
Origin: Stanley Butte, Graham Co, Arizona, United States
Sample size: 6 x 5 x 3 cm
Photo: Tom Loomis

 

Grossular
(zoom-in of above)

 

Grossular
Origin: Black Lake mine, Thetford, Quebec, Canada
Sample size: 3.5 x 3 x 2 cm
Photo: Tom Loomis

 

Grossular
(zoom-in of above)

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