Alumino-magnesiotaramite

Formula:  Na(CaNa)Mg₃Al₂(Si₆Al₂)O₂₂(OH)₂

Origin of name: From aluminum, magnesium and taramite

Crystal system:  Monoclinic

Crystal class:  2/m

Twinning:

Unit cell: a = 9.92 Å, b = 18.13 Å, c = 5.35 Å, b = 104.84°

Colour: Black, with possible tinges of blue or green

Diaphaneity: Semi-transparent

Luster: Vitreous

Habit: prismatic crystals, as grains and rims on other amphiboles

Hardness: 5-6

Specific gravity: 3.23-3.48

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

Tenacity: Brittle

Streak:

Synonyms/varieties:

Comments:  Series with magnesiotaramite and with aluminotaramite. Member of the amphibole group. Found in sodium-metasomatised alkalic gneisses and nepheline syenite dikes; in eclogite metamorphosed to the amphibolite facies.