Kaolinite

Formula:  Al₂SiO₅(OH)₄

Origin of name:  After locality; Kao-ling = high ridge, Jianxi, China

Crystal system:  Triclinic

Crystal class:  -1

Twinning: 

Unit cell: a = 5.16 Ǻ, b = 8.96 Ǻ, c = 7.41 Ǻ, α = 91.7°, β = 104.9°, γ = 89.8°

Colour:  Colourless, white, yellowish pink, reddish, bluish

Diaphaneity: 

Luster:  Pearly to dull earthy

Habit:  Thin hexagonal platelets or scales; elongated platelets or curved laths; massive compact, friable, mealy

Hardness:  2 to 2.5

Specific gravity:  2.6 to 2.63

Cleavage:  1; {001} perfect

Tenacity:  Scales flexible, inelastic, plastic

Streak: 

Synonyms/varieties:  Anauxite (SiO₂-rich var.), ancudite, carnat, collyrum, Fuller's earth

Comments:  Polymorphous with dickite, halloysite and nacrite