Volkonskoite

Formula: Ca_0.3(Cr,Mg,Fe)₂(Si,Al)₄O₁₀(OH)₂.4H₂O

Origin of name: for Petr Mikhailovich Volkonskoy (1776-1852), Russian prince, Minister of the Imperial Court, Russia.

Crystal system: Monoclinic

Crystal class: 2/m

Twinning:

Unit cell: a = 5.16, b = 8.94, c = 14.4, β = 90°

Colour: Green, olive green, bright green, yellow

Diaphaneity: Subopaque to translucent

Luster: Dull, resinous

Habit: Fine scales, fibers, massive

Hardness: 1 to 2

Specific gravity: 2.11 to 2.36

Cleavage: {001} perfect

Tenacity: Brittle, conchoidal fracture

Streak: Blue green

Synonyms/varieties: Volchonskoite, Wolchonskoite

Comments: dioctahedral smectite