Mineral Mica
"Mineral mica is the
name of a group of minerals such as
biotite, muscovite, lepidolite, zinnwaldite, phlogopite and clintonite."
Muscovite and biotite are the most common ones and also most prefect when it comes to the cleavage of mica sheets.
Muscovite Mica
Muscovite is the light-coloured mica. It is most often grey, white or colourless, but can be pinkish, or have green, yellow, violet, red or brown shades. Its crystals are pseudohexagonal and tabular, and it has got the perfect mica cleavage - it splits easily into thin sheets.
Biotite Mica
Biotite is the mafic, dark-coloured equivalent. Like muscovite, it has tabular pseudohexagonal crystals, and the micaceous cleavage which helps it to break into thin sheets. It is most often dark brown, but can be black, dark green or reddish brown. Both are found in igneous, metamorphic, and sedimentary rocks.
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