Gedrite

Formula:  (Mg, Fe)₅ Al₂ (Si₆ Al₂) O₂₂ (OH)₂

Origin of name:  After locality; Gèdre, Hautes-Pyrénées, France

Crystal system:  Orthorhombic

Crystal class:  2/m 2/m 2/m

Twinning:

Unit cell:

Colour:  White, grey, greenish, brownish green, clove-brown, yellowish brown, dark brown

Diaphaneity:  Transparent

Luster:  Vitreous to silky

Habit:  Crystals prismatic; massive, fibrous or lamellar

Hardness:  5.5 to 6

Specific gravity:  3.15 to 3.57

Cleavage:  3; {110} perfect, {010} and {100} imperfect

Tenacity:

Streak:  Colourless or greyish

Synonyms/varieties:

Comments:  Series with ferrogedrite