They are all silicate minerals, known as sheet silicates because they form in distinct layers. Micas are fairly light and relatively soft, and the sheets and flakes of mica are flexible. The most common include: purple lepidolite, black biotite, brown phlogopite and clear muscovite. Mica minerals are major rock forming minerals found in gneiss, schist and granite. The mica group includes muscovite mica and biotite mica. They usually form. The micas are an important group of minerals. They represent the classic phyllosilicate mineral and are usually the first minerals to be thought of from this.


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The crystalline structure of mica forms layers that can be split or delaminated into thin sheets usually causing foliation in micas mineral.


These sheets are chemically inert, dielectricelastic, micas mineral, hydrophilic, insulating, lightweight, platy, reflective, refractive, resilient, and range in opacity from transparent to opaque. Mica is stable when exposed to electricity, light, moisture, and extreme temperatures.

It has micas mineral electrical properties as an insulator and as a dielectric, and can support an electrostatic field while dissipating minimal energy in the form of heat; it can be split very thin 0.

Muscovite, the principal mica used by the electrical industry, is used in capacitors that are ideal for high frequency and radio frequency.

Amethyst Galleries - THE MICA GROUP

Muscovite and phlogopite are used in sheet and ground forms. The mica acts as a filler and extender, provides a smooth micas mineral, improves the workability of the compound, and provides resistance to cracking. In the paint industry, ground mica is used as a pigment extender that also facilitates suspension, reduces chalking, prevents shrinking and shearing of the paint film increases the resistance of the paint film to water penetration and weathering and brightens the tone of colored pigments.

Mica also promotes paint adhesion in aqueous and oleoresinous formulations. micas mineral

The Mica Group

The coarsely ground mica flakes help micas mineral the loss of circulation by sealing porous sections of the drill hole. The plastics industry used dry-ground mica as an extender and filler, especially in parts for automobiles as micas mineral insulation to suppress sound and vibration.

Mica is used in plastic automobile fascia and fenders as a reinforcing material, providing improved mechanical properties and increased dimensional stability, stiffness, and strength. Being true phyllosilicates, all micas are thus composed of sheets of micas mineral tetrahedrons. The silicate sheets are composed of interconnected six membered rings.

These rings are responsible for the micas typical six sided pseudohexagonal symmetry, in actuality they are only monoclinic or triclinic.

Mica Group

Each tetrahedron in the rings shares three of their oxygens with three other tetrahedrons and all the tetrahedrons in a given sheet point their unshared oxygen in the same direction. The structure of micas is stacked like a building with several different layers.

Two micas mineral layers T with their tetrahedral points pointing toward each other, sandwich small metal ions such as aluminum in an octahedral layer O. Each rainstorm brings a new layer of micas mineral that settles on the seafloor on top of the previous layers.

Each layer increases the depth of the sediment micas mineral produces heat and pressure on the sedimentary layers below Sedimentary rock formation The upper layers create downward pressure on the sedimentary layers that lie beneath them.

The upper sedimentary layers compress the moisture out of the sediments due to the weight of the overlying layers. The bottom layers turn into shale, a sedimentary rock shale due to the heat and pressure.

Phlogopitetypically brown, and paragonitewhich is macroscopically indistinguishable from muscovite, also are fairly common. Lepidolitegenerally pinkish to lilac in colour, occurs in lithium-bearing pegmatites.


Glauconitea 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 mineral except glauconite exhibit easily observable perfect cleavage into micas mineral sheets.

Glauconite, which most often occurs as pelletlike grains, has no apparent cleavage.


The names of the rock-forming micas constitute a good example of the diverse bases used in naming minerals: Compositions of the common rock-forming micas are given in the table. Few natural micas have end-member compositions. For example, most muscovites contain sodium substituting for some potassium, and diverse varieties have chromium or vanadium or micas mineral combination of both replacing part of the aluminum; furthermore, micas mineral Si: Al ratio may range from the indicated 3: Similar variations in composition are known for the other micas.

Thus, as in some of the other groups of minerals e.