Dachiardite

Formula:  (Ca,Na₂,K₂)₅Al₁₀Si₃₈O₉₆ ^. 25H₂O

Origin of name:  For A. d'Achiardi, Italian mineralogist

Crystal system:  Monoclinic

Crystal class:  2/m

Twinning:  On {001}, rare cyclic eightlings

Unit cell: a = 18.63 Å, b = 7.51 Å, c = 10.25 Å, β = 108.1°

Colour:  Colourless

Diaphaneity:  Transparent

Luster:  Vitreous

Habit:  Crystals prismatic

Hardness:  4 to 4.5

Specific gravity:  2.17 to 2.?

Cleavage:  2; {001} and {100} perfect

Tenacity:

Streak:

Synonyms/varieties:  Achiardite, svetlozarite (twinned var.)

Comments: