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All crystallize in the monoclinic system, with a tendency towards pseudohexagonal crystals, and are similar in structure but vary in chemical composition. Micas are translucent to opaque with a distinct vitreous or pearly luster, and different mica minerals display colors ranging from white to green or red to black.
Muscovite (also known as common mica, isinglass, or potash mica [6]) is a hydrated phyllosilicate mineral of aluminium and potassium with formula KAl 2 (AlSi 3 O 10)(F,OH) 2, or 2 (Al 2 O 3) 3 (SiO 2) 6 (H 2 O). It has a highly perfect basal cleavage yielding remarkably thin laminae (sheets) which are often highly elastic.
Phlogopite is a yellow, greenish, or reddish-brown member of the mica family of phyllosilicates. It is also known as magnesium mica. Phlogopite is the magnesium endmember of the biotite solid solution series, with the chemical formula KMg 3 AlSi 3 O 10 (F,OH) 2. Iron substitutes for magnesium in variable amounts leading to the more common ...
Differences in chemical composition and crystal structure distinguish the various species. Within a mineral species there may be variation in physical properties or minor amounts of impurities that are recognized by mineralogists or wider society as a mineral variety. Mineral variety names are listed after the valid minerals for each letter.
Mineral symbols (text abbreviations) are used to abbreviate mineral groups, subgroups, and species, just as lettered symbols are used for the chemical elements. The first set of commonly used mineral symbols was published in 1983 and covered the common rock-forming minerals using 192 two- or three-lettered symbols. [ 1 ]
Biotite is a common group of phyllosilicate minerals within the mica group, with the approximate chemical formula K(Mg,Fe) 3 AlSi 3 O 10 (F,OH) 2.It is primarily a solid-solution series between the iron-endmember annite, and the magnesium-endmember phlogopite; more aluminous end-members include siderophyllite and eastonite.
Fuchsite, also known as chrome mica, is a chromium (Cr)-rich variety of the mineral muscovite, belonging to the mica group of phyllosilicate minerals, with the chemical formula K(Al,Cr) 2 (AlSi 3 O 10)(OH) 2. [2] Trivalent chromium replaces one of the aluminium (Al) atoms in the general muscovite formula producing the apple green hue ...
Annite is a phyllosilicate mineral in the mica family. It has a chemical formula of KFe 3 2+ AlSi 3 O 10 (OH) 2. [8] Annite is the iron end member of the biotite mica group, the iron rich analogue of magnesium rich phlogopite. [9] Annite is monoclinic and contains tabular crystals and cleavage fragments with pseudohexagonal outlines. [6]