Dickite

Formula:  Al₂Si₂O₅(OH)₄

Origin of name:   For Allan Dick, Scottish chemist

Crystal system:   Monclinic

Crystal class:   m

Twinning:

Unit cell: 

Colour:  Colourless, white

Diaphaneity:  Transparent to translucent

Luster:  Satiny to dull earthy

Habit:   Crystals thin tabular, pseudohexagonal, minute; stacked platelets, massive, compact, friable or mealy

Hardness:   2 to 2.5

Specific gravity:   2.60

Cleavage:   1; {001} perfect

Tenacity: 

Streak: 

Synonyms/varieties:

Comments:   Polymorphous with halloysite, kaolinite and nacrite