Mineral Information and Data:

Almandine
Fe2+3Al2(SiO4)3 [CNMNC approved formula]

Named for Alabanda in Turkey, ancient gem cutting center.

IMA status : Valid species (Pre-IMA Ancient) Grandfathered
CLASSIFICATION 
Dana
(8th edition) :
51.04.03a.02  
  (51) Nesosilicate Insular SiO4 Groups Only
  (51.04) with cations in [6] and >[6] coordination
  (51.04.03a) Garnet group (Pyralspite 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 = 11.53 Å
Crystal Habit: Crystals usually dodecahedra or trapezohedra; also in combination or with hexoctahedron; massive.
Twinning: No data
  
Color: Deep red, brownish red, brownish black
Diaphaneity: Transparent to translucent
Luster: Vitreous to resinous
Hardness (Mohs): 7 to 7.5
Measured Density: 4.1 to 4.3 g/cm3
Cleavage: 1; {110} parting sometimes distinct
Tenacity: Brittle
Fracture: Subconchoidal
Streak: White
  
Polymorphism and Series: Forms two series, with pyrope, and with spessartine
Geologic Setting: The most common garnet, typically in mica schists and gneisses, from regionally
metamorphosed argillaceous sediments and pelites; also in contact metamorphic hornfels. In granites and eclogites; in sedimentary rocks; as a detrital mineral
Mineral Association: Biotite, cordierite, chlorite, staurolite, andalusite, kyanite, sillimanite, hematite,
plagioclase, amphibole, pyroxene
  
Synonyms/varieties: Almandite, carbuncle
Other Properties: Gemstone Readily Available.

 

Almandine
Origin: Fanny Gorge mine, Spruce Pine, Mitchell Co., North Carolina, U.S.A.
Sample size: Microscopic image
Photo and Owner: Lou Perloff

 

Almandine
Almandine in schist
Origin: Gaisberg Glacier, Granatenkogel, Otztal, Austria
Sample size: 11.2 x 8.0 x 4.3 cm
Photo: Rob Lavinsky

 

Almandine
(zoom-in of above)

 

Almandine
This specimen of chloritic schist hosts numerous, lustrous, dodecahedral crystals of almandine. The largest is 2.1 cm across.
Origin: Fauske, Nordland, Norway
Sample size: 11 x 7 x 2.6 cm
Photo: John Veevaert, Trinity Mineral Co

 

Almandine
(zoom-in of above)

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