Muscovite

KAl2(AlSi3O10)(F,OH)2
by

 Obie Pepper


Image taken from:
http://mineral.galleries.com/scripts/item.exe?ENLARGE+Minerals+Silicates+Muscovite+MUS-17,
a page within mineral.galleries.com.

This web page was created for a Mineralogy course, GO 336.  The content of this page was compiled to the best of my ability as a student at Emporia State University.


Contents

Introduction
    Muscovite is a common mineral found all over the world, however most locations do not produce a high yield product. Some lower quality areas do produce useful forms of muscovite though.  Muscovite is a valuable mineral, but is not known for its aesthetic beauty and is mainly used for industrial purposes, such as in heat and electrical insulators.  Its first recorded use was in Old Russia as window glass, due to muscovite's transparent crystals.  The word muscovite comes from the Old Russian word for this kind of glass, which is Muscovy-glass, and was derived from the Latin word micare, meaning to shine (Hurlbut & Klein, p. 517).  If you want to find out more, read on. This page was designed to delve into muscovite's physical properties, occurrences, and uses.

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Physical Properties

The information in this table was compiled from www.galleries.com.

Chemistry
KAl2(AlSi3O10)(F, OH)2; potassium aluminum silicate hydroxide fluoride
Class
silicates
Subclass
phylosilicates
Group
micas
Color
white, yellow, silver, green, or brown
Hardness
2-2.5
Avg. Specific Gravity
2.8
Luster
vitreous to pearly
Transparency
transparent to translucent
Cleavage 
perfect in one direction {001}; sheets or flakes with elastic quality
Fracture
uneven; rarely observed due to perfect cleavage
Streak
white
Crystal System
monoclinic; 2/m; several polytypes 2M1, 1M, 3T; 2M1 common with space group C2/c
Crystal Habits
distinct crystals rare; tabular with prominent faces {001}; can have diamond shaped prism faces up to 60 degrees {110} mimicking orthorhombic symmetry; can also have hexagonal appearance {010}; can have penetration twins with {310} at twin axis
Gem Use 
none
Field Indicators
perfect cleavage, color and associations, elasticity, crystal habit
Associated Minerals
beryl, tourmaline, quartz, feldspars
Associated Rocks Types
igneous, metamorphic, detrital sedimentary 


Image taken from:
http://mineral.galleries.com/scripts/item.exe?ENLARGE+Minerals+Silicates+Muscovite+MUS-18,
a page within mineral.galleries.com.

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Occurrences
    Muscovite is found all over the world, however, not all localities produce a high yield product.  The largest and most important deposits of muscovite are found in the CIS, Pakistan, India, and Brazil.  The United States produces only a small amount of high yield sheet mica, however, the United States leads the world in the production of scrap mica.  The major locations of scrap mica production in the United States are located in North and South Carolina, Connecticut, Mew Mexico, Georgia, and South Dakota.  Muscovite is characteristic of granite and granite pegmatites, associated with quartz and feldspars.  The micas are often found in large crystal aggregates called books, which can be many feet in length.  Micas are the major constituent of metamorphic mica schists.  In the metamorphic chlorite zone, muscovite may be a constituent in albite-chlorite-muscovite schists.  Serecite is a form of muscovite that occurs in some schistose rocks.  It occurs in these rocks as a fibrous aggregate with minute scales and a silky luster.  Serecite can also be formed as an alteration in the walls of hydrothermal veins (Hurlbut & Klein Pg. 516). Good specimen material can be found in pegmatites world wide.  Illite is another form of muscovite that is a constituent of recent sediments, soils, and some shales. Muscovite may also be associated with minerals such as tourmaline and beryl (www.2spi.com).

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Uses
    Muscovite is a valuable mineral, but it is not known for its aesthetic beauty and will never been seen as a gem.  Its first known use was in Old Russia as a glass.  This glass was termed muscovy-glass.  Muscovite was used in this purpose due to its transparent crystals and its ability to cleave into thin sheets.  Sheet muscovite is used as an insulating material in electrical apparatuses due to its dielectric and heat resistant properties (Hurbut & Klein Pg. 517).  It was also used in this fashion as furnace doors, but its use in this capacity is not as common today because of modern technology alternatives.  The low yield product that is in major production in the United States is used extensively in heat and electrical insulators.  While this form of muscovite, scrap mica, is not very costly, it is very effective.  Muscovite can be ground up and used in many products.  The ground muscovite is used in wallpaper to give it a shiny luster.  It can also be used as a glitter and in makeup in a similar fashion, as well as, a fireproofing agent, fillers, and a lubricant in oils (www.galleries.com).

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References
Klein, C., Hurlbut, C. Jr., (1993).  Manual of Mineralogy (after J.D. Dana, revised 21st edition.).  N.Y. John Wiley and Sons.

Internet:  http://www.galleries.com/minerals/silicate/muscovit/muscovit.htm

Internet:  http://www.2spi.com/catalog/submat/mic_shet-b.html

Internet Image: http://mineral.galleries.com/scripts/item.exe?ENLARGE+Minerals+Silicates+Muscovite+MUS-17, which is a page found within mineral.galleries.com/

Internet Image: http://mineral.galleries.com/scripts/item.exe?ENLARGE+Minerals+Silicates+Muscovite+MUS-18, which is a page found within mineral.galleries.com

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This page was created 4-11-01.