Swinefordite

Formula: (Ca,Na)_0.3(Li,Mg)₂(Si,Al)₄O₁₀(OH,F)₂.nH₂O

Origin of name: for Ada Swineford (1917-1993), clay mineralogist and professor of geology at Western Washington State College, Bellingham, Washinton, USA.

Crystal system: monoclinic

Crystal class: unknown

Twinning: 

Unit cell: = 5.2, b = 9, c = 13, β = 90°

Colour: light greenish gray to grayish olive, yellow

Diaphaneity: translucent to opaque

Luster: dull, earthy

Habit: small patches, thin films, pseudomorphs of spodumene

Hardness: 1

Specific gravity: 2.3-2.8

Cleavage: [001] perfect

Tenacity: 

Streak: white

Synonyms/varieties:

Comments: member of the smectite group (clay)