Micas are a group of 37 silicate minerals, phyllosilicates whose outstanding feature is that a crystal splits easily into fragile, elastic plates along perfect basal cleavage. All crystallize in the monoclinic system, often as pseudohexagonal crystals, and they are translucent to opaque with a vitreous or pearly luster and colors from white to green or red to black. Mica is common in igneous and metamorphic rock and is occasionally found as small flakes in sedimentary rock. It is particularly prominent in granites, pegmatites and schists, where books of mica several feet across have been found. Muscovite and phlogopite are the commercially important micas. Mica goes into drywall products, paints and fillers, its insulating properties make it valuable in electronics, and it is used in cosmetics and food to add shimmer.
Facts
Formation ClassSheet silicate (phyllosilicate) 3 Chemical FormulaX2Y4-6Z8O20(OH,F)4 (general mica-group formula) 1 Hardness (Mohs) Classification
Strunz Class Crystal System UseIndustrial and Abrasive 2 Wikipedia 'Mica' states this use (or use-bearing statement); earth5 pass. Connections
Associated With
Granite's own lead description names mica as one of its main constituent minerals.
Source Granite (Wikipedia)
Mica named as one of the three dominant minerals of most pegmatites.
Source Pegmatite (Wikipedia)
Mica-rich schist (mica schist) is one of the most common schist varieties.
Source Schist (Wikipedia)
Caused By
Source EBSCO Research Starters: Igneous processes, rocks, and mineral deposits
Additional Source Mica (Wikipedia)Occurrence and production
Classified As
Crystallizes In System
In Discipline
Source Mineral (Wikipedia)
Sources
1. Mica (Wikipedia)
Wikimedia FoundationClassification section
Chemically, micas can be given the general formula X2Y4-6Z8O20(OH, F)4, in which X is K, Na, or Ca or less commonly Ba, Rb, or Cs; Y is Al, Mg, or Fe or less commonly Mn, Cr, Ti, Li, etc.; Z is chiefly Si or Al, but also may include Fe3+ or Ti.
Lead section, third sentence
Mica is common in igneous and metamorphic rock and is occasionally found as small flakes in sedimentary rock.
Properties and structure
different mica minerals display colors ranging from white to green or red to black
Properties and structure, lustre
Micas are translucent to opaque with a distinct vitreous or pearly luster
Lead section, rarity
Mica is common in igneous and metamorphic rock
Lead section
Micas () are a group of silicate minerals whose outstanding physical characteristic is that individual mica crystals can easily be split into fragile elastic plates.
Mica (Wikipedia), body text
All crystallize in the monoclinic system, with a tendency towards pseudohexagonal crystals
Caused By: Fractional Crystallization, Occurrence and production
The most important sources of sheet mica are pegmatite deposits.
Caused By: Metamorphism, Occurrence and production
Flake mica comes from several sources: the metamorphic rock called schist as a byproduct of processing feldspar and kaolin resources, from placer deposits, and pegmatites.
View the Source 2. Wikidata: Mica
Wikidata Q114675
3. Mineral (Wikipedia)
Wikimedia FoundationLead sectionQuote, Lead section
In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid substance with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.
Granite (Wikipedia)
Wikimedia FoundationAssociated With: Granite, Lead sectionQuote, Associated With: Granite, Lead section
is a coarse-grained (phaneritic) intrusive igneous rock composed mostly of quartz, alkali feldspar, mica and plagioclase.
Pegmatite (Wikipedia)
Wikimedia FoundationAssociated With: Pegmatite, Lead sectionQuote, Associated With: Pegmatite, Lead section
Most pegmatites are composed of quartz, feldspar, and mica, having a similar silicic composition to granite.
Schist (Wikipedia)
Wikimedia FoundationAssociated With: Schist, Body, protolith sectionQuote, Associated With: Schist, Body, protolith section
Schist metamorphosed from mudstone is particularly common and is often very rich in mica (a mica schist).
EBSCO Research Starters: Igneous processes, rocks, and mineral deposits
EBSCO Research StartersCaused By: Fractional Crystallization, Pegmatites and hydrothermal fluidsQuote, Caused By: Fractional Crystallization, Pegmatites and hydrothermal fluids
The high water content of pegmatite fluids, some of it occurring as vapor, allows minerals such as quartz, feldspar, and mica to grow to enormous sizes, the largest of which are on the order of railway boxcars.
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