Almandine

Formula:  Fe₃Al₂(SiO₄)₃

Origin of name:  Locality; Alabanda, Turkey, a cutting centre in antiquity

Crystal system:  Cubic

Crystal class:  4/m -3 2/m

Twinning:

Unit cell:   a = 11.53 Å

Colour: Deep red, brownish red, brownish black

Diaphaneity: Transparent to translucent

Luster:  Vitreous to resinous

Habit:  Crystals usually dodecahedra or trapezohedra; also in combination or with hexoctahedron; massive.

Hardness:  7 to 7.5

Specific gravity:  4.1 to 4.3

Cleavage: 1; {110} parting sometimes distinct

Tenacity:  Brittle

Streak:  White

Synonyms/varieties:  Almandite, carbuncle

Comments:  Series with pyrope and with spessartine. Member of the garnet group. 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.