Alumino-ferrobarroisite

Formula:  (CaNa)Fe₃Al₂(Si₇Al)O₂₂(OH)₂

Origin of name:  From aluminum, iron (Latin ferrium) and barroisite

Crystal system:  Monoclinic

Crystal class:  2/m

Twinning: 

Unit cell: a = 9.76 Å, b = 17.92 Å, c = 5.29 Å, b = 104.49°

Colour: Green

Diaphaneity: Semi-transparent

Luster: Vitreous

Habit: rims on, or cores of, other mixed species amphibole crystals

Hardness:  5 to 6

Specific gravity:  2.94

Cleavage: 3; {110} perfect, {100} and {001} parting

Tenacity: Brittle

Streak:

Synonyms/varieties:

Comments:  Series with ferrobarroisite and with alumino-barroisite. Member of the amphibole group. Found in blueschist facies metamorphic rocks.