Geology Home Page
Roger Weller, geology instructor
Chemical Group: silicate- mica
Chemical Formula: KMg3(AlSi3O10)(OH)2
Color: pale yellow to brown, brownish red Streak: white to gray
Luster: vitreous to pearly, sometimes semi-metallic
Specific Gravity: 2.8 to 3
Cleavage: perfect basal cleavage (a mica)
Tenacity: tough and elastic
Mineral Associations: Phlogopite is found in ultrabasic igneous rocks, marbles,
and magnesium-rich pegmatites.
Identifying Characteristics: darker than muscovite, lighter in color than biotite
Uses: a very good electrical insulator
Occurrences: Canada; in the USA from New York, and New Jersey
Toxicity: when-swallowed- when inhaled-
Additional Information: Phlogopite sometimes shows asterism.