Crystallized Mica

Of the 28 known species of the mica group, only 6 are common rock-forming minerals.

1) Muscovite, (Potassium Mica) the common light-colored mica. It was originally called “Muscovy glass” because it came from the Muscovy province of Russia

2) Biotite, (Magnesium Iron Mica) which is typically black or nearly so, is the most abundant. Biotite was named for Jean-Baptiste Biot, a 19th-century French physicist who studied the optical properties of micas.

3) Phlogopite, (Magnesium Mica) typically brown. Its name comes from the Greek word ‘phlogopos’ for fire like, which was chosen because of the reddish glow (color and luster) of some specimens

4) Paragonite, (Sodium Mica) which is macroscopically indistinguishable from muscovite, also is fairly common. From the Greek word ‘paragon’ “to mislead,” was so named because it was originally mistaken as talc.

5) Lepidolite, (Lithium Mica) generally pinkish to lilac in color, occurs in lithium-bearing pegmatites. From the Greek word 'lepidos' meaning “scale,” was based on the appearance of the mineral’s cleavage plates

6) Glauconite, (Iron Potassium Phyllosilicate Mica) a green species that does not have the same general macroscopic characteristics as the other micas, occurs sporadically in many marine sedimentary sequences. All of these micas except Glauconite exhibit easily observable perfect cleavage into flexible sheets. Glauconite, which most often occurs as pellet like grains, has no apparent cleavage. Although typically green, was named for the Greek word for blue ‘glaucos ‘