Ferrogedrite

Formula:  (Fe,Mg)₅Al₂(Si₆Al₂)O₂₂(OH)₂

Origin of name:   From ferrous iron (Fe²⁺) and gedrite

Crystal system:  Orthorhombic

Crystal class:  2/m 2/m 2/m

Twinning:

Unit cell: 

Colour:  Greenish, brownish green, brown, greenish blue

Diaphaneity:  Transparent to nearly opaque

Luster:  Vitreous to silky, pearly on cleavage

Habit:  Crystals prismatic; massive, fibrous, lamellar

Hardness:  5.5 to 6

Specific gravity:  3.57

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

Tenacity: 

Streak:  Colourless or grayish

Synonyms/varieties:

Comments:  Series with gedrite