Phlogopite (Potassium magnesium aluminum silicate hydroxide) is a greenish- or reddish-brown member of the mica family of phyllosilicates. It is also known as magnesium mica. Phlogopite is a rarer member of the mica group and is not well known even by mineral collectors.
Phlogopite, like other micas, has a layered structure of magnesium aluminum silicate sheets weakly bonded together by layers of potassium ions. These potassium ion layers cause the perfect cleavage in one direction that produces thin sheets or flakes . Hardness is 2.5 - 3. Specific Gravity is approximately 2.9. Phlogopite comes from the Kola Pennisula area of Russia, but notable occurences include also Ontario and Quebec.