Mount Mica Quarry, Paris, Oxford Co., Maine, USA © Van King

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


Locality: Bennett Quarry, Buckfield, Oxford Co., Maine, USA FOV: 4mm Copyright © Bill Bunn
Locality: Strickland Quarry (Eureka Quarry), Strickland pegmatite (Strickland-Cramer Quarry; Strickland-Cramer Mine; Strickland-Cramer Feldspar-Mica Quarries), Collins Hill, Portland, Middlesex Co., Connecticut, USA FOV: 15 mm Copyright © Harold Moritz
Locality: Tamminen Quarry, Greenwood, Oxford Co., Maine, USA FOV: 1cm Copyright © Bill Bunn
Locality: Bennett Quarry, Buckfield, Oxford Co., Maine, USA Copyright © Peter Cristofono