Preobrazhenskite

Formula: Mg₃B₁₁O₁₅(OH)₉

Origin of name: for P. Preobrazhensk, Russian geologist

Crystal system: orthorhombic

Crystal class: 2/m 2/m 2/m

Twinning: 

Unit cell: a = 16.33 Å, b = 9.16 Å, c = 10.59 Å

Colour: colourless, lemon-yellow, dark gray

Diaphaneity: Transparent to translucent

Luster: Vitreous

Habit: massive, fine-grained, nodular

Hardness: 4.5 to 5

Specific gravity: 2.45

Cleavage: none

Tenacity: 

Streak: White

Synonyms/varieties:

Comments: