Cochise College          Photos of Minerals

                          Geology Home Page                

                          Roger Weller, geology instructor

                          wellerr@cochise.edu
                                  copyright 2007-R.Weller

 

Mineral Information on:
phlogopite


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

 

Hardness:  2.5               Specific Gravity:  2.8 to 3                  Fracture:

Cleavage: perfect basal cleavage (a mica)
 

Tenacity:  tough and elastic

 

Crystal Forms:  Monoclinic system

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.