Cookeite

Formula:  LiAl₄(Si₃Al)O₁₀(OH)₈

Origin of name:  For J. Cooke, Jr., American chemist

Crystal system:  Triclinic

Crystal class:  -1

Twinning:

Unit cell:

Colour:  White, pink, greenish, yellowish, brown

Diaphaneity:  Transparent to translucent

Luster:  Pearly to silky

Habit:  Crystals pseudo-hexagonal plates; radial arrangements of scales, curved, small spherulites

Hardness:  2.5 to 3.5

Specific gravity:  2.58 to 2.69

Cleavage:  1; {001} perfect, micaceous

Tenacity:

Streak:

Synonyms/varieties:

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