Phlogopite Phlogopite crystal in volcanic rock from Aln . Crystal system Monoclinic. Also as irregular mica books.
Cleavage Basally perfect, producing thin flakes.
Hardness 2.5-3 Density 2.9 Color Pale greenish, yellowish brown to brown, transparent to translucent. Luster Vitreous to pearly. A little rarer member than the other micas but not uncommon. It's been mined for it's good heat and electrical insulating properties. Occurance Common in dolomites and metamorphic limestones.