Amicite

Formula:  K₂Na₂Al₄Si₄O₁₆ ^. 5H₂O

Origin of name:  For Giovan Amici (1786-1863), Italian astronomer and optician, inventor of microscope optical elements

Crystal system:  Monoclinic

Crystal class: 2

Twinning:

Unit cell:  a = 10.26 Å, b = 10.43 Å, c = 9.90 Å, b = 89°

Colour:  Colourless

Diaphaneity:  Transparent

Luster:  Vitreous

Habit:  Radial aggregates of 100-200 um crystals

Hardness:  4.5

Specific gravity:  2.06-2.23

Cleavage:  None

Tenacity:

Streak:  White

Synonyms/varieties:

Comments: Member of the zeolite group. Formed in veinlets cutting melilite-nephelinite volcanic rocks and pyroclastics; in natrolite veinlets cutting ijolite-urtite pegmatites and apatite-nepheline rocks