Claucophane

Formula:  Na₂(Mg,Fe)₃Al₂Si₈O₂₂(OH)₂

Origin of name:   Form Greek glaukos = bluish green and phainesthai = to appear

Crystal system:  Monoclinic

Crystal class:  2/m

Twinning:

Unit cell:

Colour:  Grayish, bluish black, lavender, blue, azure blue

Diaphaneity:  Translucent

Luster:  Vitreous to dull, pearly

Habit:  Crystals slender prismatic; massive; fibrous, columnar, granular

Hardness:  6

Specific gravity:  3.08 to 3.15

Cleavage:  1; {110} perfect

Tenacity:

Streak:  Grayish blue

Synonyms/varieties:

Comments:  Series with ferroglaucophane and with crossite