Chemical Formula: (Al2Li)Al2(AlSi3O10)(OH)8
Locality: Oxford Co., Maine, USA. Pala, San Diego Co., California, USA.
Name Origin: Named for Josiah B. Cooke, Jr. (1827-1894), American mineralogist and chemist, Harvard University, Cambridge, Massachusetts, USA.
Cookeite (pronounced Cook-ite) is an uncommon member of the Chlorite group, and is best known for its occurrence in granite pegmatites associated with Tourmaline, where it often forms as a growth layer upon the Tourmaline. Cookeite is named in honor of Josiah Parsons Cooke Jr. (1827-1894), a Harvard University scientist who was instrumental in the measurement of atomic weights.
Physical Properties of Cookeite
Cleavage: {001} Perfect
Color: White, Green, Brown, Yellowish white, Pinkish white.
Density: 2.67
Diaphaneity: Transparent to translucent
Fracture: Flexible – Flexible fragments.
Hardness: 2.5 – Finger Nail
Luminescence: Non-fluorescent.
Luster: Vitreous (Glassy)
Streak: white
Photos
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