Phlogopite is a mineral from the group of micas of the biotite-phlogopite isomorphic series. The largest crystal was found in Canada and weighed 330 tons.
You can see phlogopite stone for sale and buy it in the Minerals of Russia online store.
General | |
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Category | Mica, phyllosilicates |
Formula (repeating unit) |
KMg3(AlSi3O10)(F,OH)2 |
IMA symbol | Phl |
Strunz classification | 9.EC.20 |
Crystal system | Monoclinic |
Crystal class | Prismatic (2/m) (same H-M symbol) |
Space group | C2/m |
Identification | |
Color | Brown, brownish red, dark brown, yellow, yellowish brown, green, white and gray |
Crystal habit | Tabular, scaly masses, rarely perfect phenocryst tablets |
Twinning | Composition twinning |
Cleavage | Perfect basal (001) |
Fracture | None |
Tenacity | Tough, flexible thin laminae |
Mohs scale hardness | 2–2.5 |
Luster | Pearly, sometimes slightly metallic on cleavage surfaces |
Streak | White |
Diaphaneity | Transparent to translucent |
Specific gravity | 2.78–2.85 |
Optical properties | Biaxial (-), 2V=12 |
Refractive index | nα = 1.530–1.573 nβ = 1.557–1.617 nγ = 1.558–1.618 |
Birefringence | δ =0.0280–0.0450 |
2V angle | 16–20° |
Other characteristics | Fluorescent |