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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.
Normative mineralogy is an estimate of the mineralogy of the rock. It usually differs from the visually observable mineralogy, at least as much as the types of mineral species, especially amongst the ferromagnesian minerals and feldspars, where it is possible to have many solid solution series of minerals, or minerals with similar Fe and Mg ratios substituting, especially with water (e.g ...
Minerals are distinguished by various chemical and physical properties. 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.
QAPF diagram for classification of plutonic rocks. A QAPF diagram is a doubled-triangle plot diagram used to classify intrusive igneous rocks based on their mineralogy.The acronym QAPF stands for "Quartz, Alkali feldspar, Plagioclase, Feldspathoid (Foid)", which are the four mineral groups used for classification in a QAPF diagram.
Structure of illite mica – USGS [5]. Illite, also called hydromica or hydromuscovite, [6] is a group of closely related non-expanding clay minerals. Illite is a secondary mineral precipitate, and an example of a phyllosilicate, or layered alumino-silicate.
Roscoelite is a green mineral from the mica group that contains vanadium. The chemical formula is K(V 3+, Al, Mg) 2 Al Si 3 O 10 (OH) 2. [2] Crystals of roscoelite take on the monoclinic form, and are from the 2/m point group. The appearance is semi transparent to translucent coloured olive brown to green brown. The lustre is pearly.
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 ...