Phlogopite in Calcite Franklin, Sussex Co., New Jersey, USA Small Cabinet, 8.6 x 7.1 x 6.4 cm “Courtesy of Rob Lavinsky, The Arkenstone,”
Chemical Formula: KMg3(AlSi3O10)(OH,F)2
Name Origin: From the Greek flogopos – “resembling fire.”Phlogopite is a yellow, greenish, or reddish-brown member of the mica family of phyllosilicates. It is also known as magnesium mica.Phlogopite is the magnesium endmember of the biotite solid solution series, with the chemical formula KMg3(AlSi3O10)(OH,F)2. Iron substitutes for magnesium in variable amounts leading to the more common biotite with higher iron content. For physical and optical identification, it shares most of the characteristic properties of biotite.


Discovery date : 1841
Town of Origin: ANTWERP, NEW YORK
Country of Origin : USA

Optical properties

Optical and misc. Properties : Luminescent, fluorescent  –   Flexible  –   Elastique  –   Tenace  –   Transparent  –   Translucide  –   Macles possibles
Refractive Index : from 1,53 to 1,63
Axial angle 2V: 0-15°

Physical properties

Hardness : from 2,00 to 3,00
Density: from 2,78 to 2,85
Color : yellowish brown; brownish red; colorless; white; greenish; grey; brown yellow; blackish; whitish; green
Luster : submetallic; nacreous
Streak : white
Cleavage : Yes


Flogopite San Vito quarry, Monte Somma, Campania, Italy Specimen weight:52 gr. Crystal size:1 mm Overall size: 53mm x 32 mm x 33 mm © minservice
Phlogopite Bancroft, Ontario, Canada Cabinet, 34.7 x 26.3 x 1.6 cm © ircoks