Ilvaite

Formula:  CaFe₂FeSi₂O₇O(OH)

Origin of name:  Locality; Isle of Elba (Ilva in Latin)

Crystal system:  Orthorhombic

Crystal class:  2/m 2/m 2/m

Twinning: 

Unit cell: a = 13.01 Ǻ, b = 8.81 Ǻ, c = 5.85 Ǻ

Colour:  Black to grayish black

Diaphaneity: 

Luster:  Vitreous to submetallic

Habit:  Crystals thick prismatic, diamond-shaped cross section, vertically striated; massive, compact or columnar

Hardness:  5.5 to 6

Specific gravity:  3.8 to 4.1

Cleavage:  2; {001} and {010} distinct

Tenacity:  Uneven; brittle

Streak:  Black, brownish or greenish tint

Synonyms/varieties:  Jenite, lievrite, yenite

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