Cleaved crystals of Phlogopite showing their pseudohexagonal shape.
CHEMISTRY KMg33102SiAlO(F,OH) Potassium magnesium aluminosilicate of fluorine
CRYSTALLOGRAPHY Monoclinic
CRYSTAL GROWTH AND HABITS Crystals of Phlogopite are usually six sided prismatic to tabular and appear pseudohexagonal. It can also occur as coarse grained platy or scaly masses.
COLOR AND OTHER OPTICAL PROPERTIES Phlogopite is normally some shade of brown ranging from reddish to yellowish. It may also be greenish to whitish. It is transparent to translucent.
HARDNESS 2 -3 SPECIFIC GRAVITY 2.7-2.8
LUSTER Sub vitreous to pearly or even sub metallic on cleavage faces
STREAK White
BREAKABILITY Perfect cleavage in one direction producing thin elastic sheets.
OCCURRENCE Phlogopite is found in ultramafic igneous rocks like kimberlites and peridotites. It is also produced by the metamorphism of magnesium rich carbonates like dolomite.
ASSOCIATED MINERALS Dolomite, Calcite, Tremolite, Scapolite, Epidote, Augite, Magnetite