THE MINERAL MUSCOVITE

  • Chemistry: KAl2(AlSi3O10)(F, OH)2, Potassium aluminum silicate hydroxide fluoride.
  • Class: Silicates
  • Subclass: Phyllosilicates
  • Group: Micas
  • Uses: heat and electrical insulator for industrial purposes.
  • Specimens

Muscovite is a common rock forming mineral and is found in igneous, metamorphic and detrital sedimentary rocks. Muscovite has a layered structure of aluminum silicate sheets weakly bonded together by layers of potassium ions. These potassium ion layers produce the perfect cleavage of muscovite. Although it has such easy cleavage, the cleavage sheets are quite durable and are often found in sands that have undergone much erosion and transport that would have destroyed most other minerals. The sheets of muscovite also have high heat and electrical insulating properties and are used to make many electical components. Muscovite sheets were used for kitchen oven windows before synthetic materials replaced them.

Muscovite is not often valuable as a mineral specimen but is often associated with other minerals of extrodinary beauty and value. Some very nice muscovite crystals accompany such valuable minerals as tourmaline, topaz, beryl, almandine and others. A rare twin variety from Brazil forms yellow five pointed stars and is called "Star Muscovite". A deep green variety is called fuchsite and is colored by chromium inpurities.

PHYSICAL CHARACTERISTICS:

  • Color is white, silver, yellow, green and brown.
  • Luster is vitreous to pearly.
  • Transparency crystals are transparent to translucent.
  • Crystal System is monoclinic; 2/m
  • Crystal Habits include tabular crystals with a prominant pinacoid termination. Muscovites four prism faces form diamond shaped "books" and if modified by another pinacoid they form pseudo-hexagonal crystal "books". The sides of the crystal often tend to tapper. Also as lamellar rock forming masses and small flakes in detrital matterial. Twinned crystals can form flat five pointed stars.
  • Cleavage is perfect in one direction producing thin sheets or flakes.
  • Fracture is not readily observed due to cleavage but is uneven.
  • Hardness is 2 - 2.5.
  • Specific Gravity is approximately 2.8 (average)
  • Streak is white.
  • Associated Minerals are quartz, feldspars, beryl and tourmalines.
  • Other Characteristics: cleavage sheets are flexible and elastic, meaning they can be bent and will flex back to original shape.
  • Notable Occurrences include India, Pakistan, Brazil and many USA locallities.
  • Best Field Indicators are crystal habit, cleavage, elastic sheets, color and associations.
MUSCOVITE specimens:
(hover for more info)
MUSCOVITE specimen mus-1
$ 60.00
Dims: 3-1/2" x 2-3/4" x 2"
Wt: 7.4 oz
Minas Gerais, Brazil
It's all Muscovite; there is no host rock, and most of it has good crystal form. This piece is basically a cluster of Muscovite books, the largest one being 1-1/4 inch high, 2-1/2 inches long, and 1/8 inch thick. It shows partial crystal form, especially on its less-exposed basal face. Most of the smaller books in the cluster show good hexagonal shape. All are the standard translucent/transparent pale green-brown of this mica variety. Its got a good sparkle!
no photo
mus-1 ($ 60.00)
Minas Gerais, Brazil
MUSCOVITE specimen mus-3
$ 35.00
Dims: 5-1/2" x 3-1/2" x 2"
Wt: 1 lb., 4 oz
unknown
A rather unusual form of Muscovite, this specimen has a deep red color similar to that of Garnet. If I'm not mistaken, the color is caused by traces of cobalt. Though showing no crystal form and visible folding and creasing, it does show lots and lots of micaceous layering, and the standard, pearly luster. There are also small layers of quartz sandwiched in. This is some rather unusual material!
no photo
mus-3 ($ 35.00)
unknown
MUSCOVITE specimen mus-4
$ 40.00
Dims: 4-1/4" x 5" x 1"
Wt: 15.5 oz
unknown
This strange Muscovite variety has a wine-red color akin to that of some garnets. Other than the color, it displays all of the characteristics of standard Muscovite. The lack of discernable crystal form is likely caused by the color-giving impurities, and insured by the presence of quartz sandwiched between layers. Neat stuff!
no photo
mus-4 ($ 40.00)
unknown
MUSCOVITE specimen mus-5
$ 27.50
Dims: 2" x 1-1/4" x 1-1/2"
Wt: 15.7 g
Aldeia do Eme, Minas Gerais, Brazil
I really like this specimen because of its simplicity. There's not a lot of intersecting and incomplete books, or other materials to convolute or interrupt the formation. We have 2 books of Muscovite, one complete, that intersect at each other's edges. The complete book has excellent form, and smaller hexagonal crystals stacked up on both its basal faces, producing attractive designs on them. Their color is a reddish brown, and they have the classic pearly, micaceous luster.
no photo
mus-5 ($ 27.50)
Aldeia do Eme, Minas Gerais, Brazil
MUSCOVITE specimen mus-6
$ 42.00
Dims: 4.5" x 4.5" x 3.4" (11.4 x 11.4 x 8.6 cm)
Wt: 1 lb., 3.9 oz. (562 g)
Minas Gerais, Brazil
One of our larger available Muscovite specimens, this piece consists of a matrix of white, semicrystalline albite that houses several black tourmaline crystals, tiny crystals of either apatite or beryl, and dozens of large, well-formed books of brownish Muscovite. These books range from 3 mm to over 1" (2.5 cm) in diameter. They are in relatively good condition, though many of the more exposed books have damaged edges. All show good hexagonal tabular form, a pearly luster, and dim translucence. There is a lot of Muscovite in this specimen!
no photo
mus-6 ($ 42.00)
Minas Gerais, Brazil
MUSCOVITE specimen mus-7
$ 34.00
Dims: 1.8" x 1.5" x 1.4" (4.6 x 3.8 x 3.6 cm)
Wt: 1.59 oz. (45.1 g)
Divino das Laranjeiras, Minas Gerais, Brazil
Several books of "star-twin" Muscovites rest on the albite host rock of this small hand specimen. They show only a small amount of damage and range in size from less than 0.3" (8mm) to 1.0" (2.5 cm) in diameter. Their shape is that of a hexagram, or "Star of David", and none are complete due to their intergrowth with the albite host rock and each other. These crystals have all of the characteristics of Muscovite, including the flaky, micaceous consistency, the greenish-yellow coloration, and the pearly luster. The albite host rock is crystalline, but only a small portion shows any definite crystal form.
no photo
mus-7 ($ 34.00)
Divino das Laranjeiras, Minas Gerais, Brazil
MUSCOVITE specimen mus-8
$ 38.00
Dims: 2.0" x 1.7" x 1.5" (5.1 x 4.3 x 3.8 cm)
Wt: 2.58 oz. (73.2 g)
Divino das Laranjeiras, Minas Gerais, Brazil
This specimen boasts several intergrown books of "star twin" Muscovite, which forms hexagram-shaped books through cyclic twinning. Other than their unusual shape, these books are just like any other Muscovite formations in the fact that they have a flaky consistency due to excellent basal cleavage, a pearly luster, and a greenish-yellow color. One of the books in particular shows considerable damage, but the rest are in very good or excellent condition. The albite host rock on which they grow is white and has a dull luster. It has crystalline tendencies, but shows no definite form.
no photo
mus-8 ($ 38.00)
Divino das Laranjeiras, Minas Gerais, Brazil
MUSCOVITE specimen mus-9
$ 36.00
Dims: 7.0" x 5.4" x 0.1" (17.8 x 13.7 x 0.2 cm)
Wt: 3.67 oz. (104.0 g)
Minas Gerais, Brazil
This odd specimen consists of a single large "book" of Muscovite. It shows a warped but complete pseudohexagonal form, and some of its edges are truncated by angled faces that have a very strange texture; they almost seem as if they had been ground down with a sanding belt or a grinding wheel, but such actions would have made the surfaces disseminate, bend, and flake. It has the standard pale brown color, pearly luster, and micaceous consistency that one expects of Muscovite and shows a very dim but noticeable transparence. What drew us to this piece is the fact that it has a warped and incomplete crystal of elbaite tourmaline running through half of it! It does show a triangular or hexagonal cross-section, though, and its visible faces are well-defined where intact and show a vitreous luster. In moderate light the crystal appears black and opaque, but in bright light or sunlight one can see its deep blue-green color and some areas of transparence.
no photo
mus-9 ($ 36.00)
Minas Gerais, Brazil
MUSCOVITE specimen mus-10
$ 35.00
Dims: 4.5" x 2.6" x 2.0" (11.4 x 6.6 x 5.1 cm)
Wt: 8.04 oz. (227.9 g)
Minas Gerais, Brazil
This ample hand specimen consists of a profusion of intergrown hexagonal "books" of Muscovite platelets. Surprisingly, only one book appears to show any visible damage. The largest has a diameter of 1.9" (4.8 cm) and a thickness of 0.3" (8 mm), and like all of the others, has a pale reddish-brown coloration and a pearly luster on its faces. Their form is excellent, and only the smaller books are thin enough to be able to transluce light. There is a very small amount of what I believe is white calcite attached to one spot on the specimen, which is likely the remains of its host rock.
no photo
mus-10 ($ 35.00)
Minas Gerais, Brazil
MUSCOVITE specimen mus-11
$ 30.00
Dims: 4.0" x 3.4" x 2.6" (10.2 x 8.6 x 6.6 cm)
Wt: 15.0 oz. (424 g)
Minas Gerais, Brazil
This hand specimen consists of dozens of hexagonal "books" of Muscovite that show moderate damage and generally good form. The largest of these books has dimensions of 1.8 x 1.5 x 0.1" (4.6 x 3.8 x 0.3 cm) and is incomplete due to heavy intergrowth. All have the standard pale brown coloration and pearly luster that are standard for this mineral, and though most books are essentially opaque, a few of the smaller, thinner books show definite translucence. There are patches of albite present on the specimen, and there is likely a "core" of this or another mineral at the center of the cluster, which would explain its heaviness.
no photo
mus-11 ($ 30.00)
Minas Gerais, Brazil
MUSCOVITE specimen mus-12
$ 30.00
Dims: 4.8 x 3.0 x 2.7" (12.2 x 7.6 x 6.9 cm)
Wt: 11.7 oz. (333 g)
Minas Gerais, Brazil
This generous hand specimen consists mostly of a cluster of intergrown Muscovite "books". These books have dimensions that measure as large as 1.5 x 1.0 x 0.2" (3.8 x 2.5 x 0.5 cm), and very few of them show any appreciable damage. All have moderately good pseudohexagonal form, though none of them show a regular, symmetrical hexagonal shape. They have all of the standard characteristics of Muscovite, including a pale brown color, a pearly luster, and a flaky, micaceous consistency. Some of the thinner books show a dim transparence, but most are translucent or opaque. There is a small amount of a dull gray host rock present on the piece, but it is only enough to form somewhat of a base.
no photo
mus-12 ($ 30.00)
Minas Gerais, Brazil
MUSCOVITE specimen mus-13
$ 45.00
Dims: 3.4 x 3.0 x 2.7" (8.6 x 7.6 x 6.9 cm)
Wt: 12.7 oz. (361 g)
Minas Gerais, Brazil
This rather odd specimen consists of many intergrown hexagonal Muscovite "books" that extend from an apatite base. The books are generally in very good condition, though several of the more exposed ones show obvious damage. The smaller books have excellent hexagonal shapes, with well-defined edges and clean faces, but most of the larger books are somewhat malformed, with some of them being almost formless. All have the standard pale brown coloration and pearly luster, and the micaceous, flaky consistency of Muscovite. Though a few of the thinner books are translucent or even dimly transparent, most are thick enough to be essentially opaque. Their base is worthy of study by itself, as it is made up of a single, incomplete and malformed apatite crystal. Its color ranges from a pale to a moderately dark greenish-gray and its luster is dull and waxy at best. The material is thoroughly opaque.
no photo
mus-13 ($ 45.00)
Minas Gerais, Brazil
MUSCOVITE specimen mus-14
$ 75.00
Dims: 5.6 x 3.9 x 3.3" (14.2 x 9.9 x 8.4 cm)
Wt: 1 lb., 5.6 oz. (613 g)
Minas Gerais, Brazil
Scores of intergrown Muscovite "books" make up the bulk of this large hand specimen. While many of the more exposed books show obvious damage, an impressive number are intact. They achieve diameters of 1.5" (3.8 cm) or more and thicknesses of 0.1" (3 mm). Their form is generally very good, as most of the intact books have a regular hexagonal outline. Their edges are well-defined and their faces are smooth and clean, possessing the standard pearly luster. All have a brown color with a subtle red tinge, and though some of the thinner books may be translucent, most are essentially opaque. Besides the Muscovite there are a number of dark green-brown apatites that are in good condition and have moderately good hexaogonal prismatic form. They have a bright, vitreous luster and are opaque. There is no host rock present on the specimen.
no photo
mus-14 ($ 75.00)
Minas Gerais, Brazil
MUSCOVITE specimen mus-15
$ 75.00
Dims: 4.0 x 3.5 x 2.8" (10.2 x 8.9 x 7.1 cm)
Wt: 10.6 oz. (301.0 g)
Minas Gerais, Brazil
This moderately sized hand specimen consists of a cluster of partly intergrown hexagonal Muscovite "books". Several of the more exposed books are noticeably damaged or even broken, but most are intact and in excellent condition. All have very good pseudohexagonal tabular form, with well-defined edges and clean faces that possess the standard pearly luster. All have a pale brown coloration with a subtle red hint and are only very dimly translucent at best. There is a small amount of amorphous, massive and milky-white calcite attached to a portion of the cluster.
no photo
mus-15 ($ 75.00)
Minas Gerais, Brazil
MUSCOVITE specimen mus-16
$ 36.00
Dims: 6.7 x 3.9 x 3.1" (17.0 x 9.9 x 7.9 cm)
Wt: 2 lbs., 0.5 oz. (920 g)
Minas Gerais, Brazil
Scores of intergrown Muscovite "books" make up this specimen. They achieve maximum dimensions of 1.6 x 1.2 x 0.2" (4.1 x 3.1 x 0.5 cm) and are in fair condition, as many of the exposed blades are damaged or incomplete due to breakage. Those that are intact, however, show very good pseudohexagonal tabular form, with well-defined edges and generally clean faces that possess the standard pearly luster. All have a moderate brown coloration with a hint of red, and only the thinnest of the books are translucent- most are opaque, though individual flakes are transparent. They are attached to a greenish-brown base that sparkles with thousands of tiny, embedded Muscovite platelets. Though it is not evident, I believe that the bulk of this base is made up of a single, large apatite crystal that was coated heavily with the tiny platelets before the larger books formed. There are also many tiny hexagonal apatite prisms partly embedded in and scattered about the formation of larger books. They do not exceed 0.1" (3 mm) along any axis, and have excellent form and an almost vitreous luster. They are also transparent and clear, but have a green color similar to that of the base. There is also a small amount of warped, crystalline albite attached to one end of the base, along with more Muscovite.
no photo
mus-16 ($ 36.00)
Minas Gerais, Brazil
MUSCOVITE specimen mus-17
$ 38.00
Dims: 7.2 x 4.4 x 1.6" (18.3 x 11.2 x 4.1 cm)
Wt: 1 lb., 9.3 oz. (718 g)
Disputed Mine, Harts Range, Northern Territories, Australia
This large "book" of crystalline Muscovite confuses me a bit- I cannot tell whether it simply has a very good monoclinic bladed form, or if the book is mirror-twinned, with the twinning plane running along its length. Most likely it is the former, as the twinning plane is not definite. The book shows little damage and is in excellent condition, and has a warped but still reasonably good form, with some well-defined edges and clean faces. It has the classic micaceous, flaky consistency and pearly luster that one expects of this mineral, and has a moderately pale to deep brown coloration. The book is essentially opaque, though tiny areas at its thinnest edges show a translucence or dim transparence. There are tiny bits of an albite crust present at its thick end- these are dull in luster and heavily rust stained- but no actual base or host rock is present.
no photo
mus-17 ($ 38.00)
Disputed Mine, Harts Range, Northern Territories, Australia
MUSCOVITE specimen mus-18
$ 60.00
Dims: 2.7 x 2.2 x 1.8" (6.9 x 5.6 x 4.6 cm)
Wt: 4.15 oz. (117.7 g)
Divino das Laranjeiras, Minas Gerais, Brazil
This small hand specimen consists of scores of small "books" of Muscovite blades that are clustered around a crystalline quartz base. Though several books are damaged, most are intact and in excellent condition. They reach maximum dimensions of about 0.8 x 0.4" (2.0 x 1.0 cm), and have excellent monoclinic bladed form, with sharp edges and clean faces. They have the classic pearly luster and a dull green-yellow coloration that is common for specimens from this locality. The books are translucent to dimly transparent, depending on their thickness, and are gathered around at least 2 hexagonal quartz prisms that appear to have good form and are transparent and clear.
no photo
mus-18 ($ 60.00)
Divino das Laranjeiras, Minas Gerais, Brazil
MUSCOVITE specimen mus-19
$ 60.00
Dims: 4.2 x 3.9 x 1.6" (10.7 x 9.9 x 4.1 cm)
Wt: 10.54 oz. (299.2 g)
Minas Gerais, Brazil
Several small blades and pseudohexagonal "books" of Muscovite rest on the albite host rock of this hand specimen. The books are in excellent condition, showing very little damage, and have dimensions of up to 2.0 x 0.9 x 0.3" (5.1 x 2.3 x 0.8 cm). The individual Muscovite blades are mostly damaged or broken, but several are still intact. All have excellent monoclinic bladed form with well-defined edges and clean faces. They have the classic pale greenish-gray color and bright pearly luster of their species and range from opaque to dimly transparent depending on their thickness. The albite base on which they restis of the variety known as Cleavelandite, and takes on the form of many intergrown pseudohexagonal blades. Though there is much damage, a surprising number of these blades are intact and show excellent form. All have a milky-white coloration and a pearly luster, and are translucent to dimly transparent. They, in turn, rest upon crystals of the more common variety of albite that has the standard monoclinic prismatic form.
no photo
mus-19 ($ 60.00)
Minas Gerais, Brazil
MUSCOVITE specimen mus-20
$ 26.00
Dims: 4.7 x 3.0 x 1.7" (11.9 x 7.6 x 4.3 cm)
Wt: 1 lb., 0 oz. (455 g)
North Bay, Ontario, Canada
This large hand specimen consists of a shapeless chunk of compacted Muscovite books and particles. This Muscovite shows neither crystal form nor definable damage due to its shapelessness and compact nature, but has some classic characteristics of Muscovite, such as a bright pearly luster and a very flaky texture. Its deep brownish-red coloration is unusual, and I have not seen it in pieces from any other locality. A substantial amount of similarly-colored quartzite is also present. There appear to be several thin layers of the Muscovite that permeate this quartzite.
no photo
mus-20 ($ 26.00)
North Bay, Ontario, Canada
MUSCOVITE specimen mus-21
$ 100.00
Dims: 4.1 x 3.6 x 2.5" (10.4 x 9.2 x 6.3 cm)
Wt: 1 lb., 4.2 oz. (574 g)
Barra do Salinas, Minas Gerais, Brazil
This display piece consists of at least 3 intergrown Muscovite "books" that are generally in very good condition. These books show reasonably good monoclinic bladed form and have the standard micaceous basal parting of all members of the mica group. Their color is extraordinary - each book consists of a "core" of material that has a pale pink or lavender coloration, off of which grew more material with the standard yellow-gray color of Muscovite. I do not know if the pink material is actually lepidolite. A small amount of quartz or quartzite is present on the piece, but it is almost entirely Muscovite by mass.
no photo
mus-21 ($100.00)
Barra do Salinas, Minas Gerais, Brazil
MUSCOVITE specimen mus-22
$ 37.50
Dims:4.5x3.3x2.8" (11.4x8.4x7.1 cm)
Wt: 13.8oz. (392g)
Coronel Murta, Minas Gerais, Brazil
This specimen consists of several "books" of muscovite crystals on a piece of massive quartz matrix. These muscovite crystals display an interesting panoply of colors, from silvery-white to pink, and dark honey color to a reddish orange in places. These muscovite crystals grow to 3.2" (8.1cm). This specimen shows only minor damage.
no photo
mus-22 ($ 37.50)
Coronel Murta, Minas Gerais, Brazil
MUSCOVITE specimen mus-23
$ 75.00
Dims:5.3x4.0x2.6" (13.5x10.1x6.6 cm)
Wt: 31.0oz. (879g)
Ouro Fino Mine, Coronel Murta, Minas Gerais, Brazil
This is a large cluster of muscovite mica crystals with a small amount of albite scattered about the piece. This specimen is most unusual-when I first glanced at it, I thought that the muscovite crystals had an alteration rind covering them. Upon examination, however, what appeared to be an alteration rind is actually a secondary growth of muscovite crystals, these being much smaller. This effect can be observed on the bottom of the specimen, and on one of the top faces. The largest crystal on this specimen measures 3.3" (8.4cm) in length. There is no damage to this specimen per se, breaks on the bottom and one of the top faces serve to show the unusual secondary growth.
no photo
mus-23 ($ 75.00)
Ouro Fino Mine, Coronel Murta, Minas Gerais, Brazil
MUSCOVITE specimen mus-24
$ 53.00
Dims:5.0x3.5x3.5" (12.7x8.9x8.9 cm)
Wt: 18.9oz. (538g)
Ouro Fino Mine, Coronel Murta, Minas Gerais, Brazil
This is another cluster of muscovite crystals exhibiting an unusual secondary growth. There is some minor albite associated with this specimen. The large muscovite crystals (to 1.4", 3.6cm) are coated with a rind of tiny muscovite crystals. This rind is 0.2" (0.5cm) in thickness. What would normally be considered damage on this specimen only serves to illustrate this secondary growth. A most unusual specimen.
no photo
mus-24 ($ 53.00)
Ouro Fino Mine, Coronel Murta, Minas Gerais, Brazil
MUSCOVITE specimen mus-26
$ 75.00
Dims: 5.16x3.46x1.50" (13.09x8.78x3.80cm)
Wt: 15.06oz (427g)
Ouro Fino Mine, Coronel Murta, Minas Gerais, Brazil
This is a beautiful muscovite specimen. A base of very pale brown muscovite (with triangular and/or hexagonal outlines) is almost completely covered with a thick layer of smaller green muscovite crystals. All are translucent (transparent in individual sheets), and the green has an especially bright vitreous luster. There is also a moderate amount of creamy off-white albite adding contrast to the slightly yellow-green of the muscovite.
no photo
mus-26 ($ 75.00)
Ouro Fino Mine, Coronel Murta, Minas Gerais, Brazil
MUSCOVITE specimen mus-25
$ 60.00
Dims: 6.05x5.14x2.76in (15.37x13.05x7.00cm)
Wt: 66.91oz (1897g)
Ouro Fino Mine, Coronel Murta, Minas Gerais, Brazil
This is a very aesthetic specimen of nice purple muscovite on a base of massive cleavelandite. Handle with care - this is a fragile mineral, and easily flakes off.
no photo
mus-25 ($ 60.00)
Ouro Fino Mine, Coronel Murta, Minas Gerais, Brazil
MUSCOVITE specimen mus-28
$ 48.00
dims mm=115.95x94.07x54.81
wt g=479
Ouro Fino Mine, Coronel Murta, Minas Gerais, Brazil
This is an excellent muscovite specimen. At its core are large crystals of a pinkish muscovite, the individual sheets of which appear transparent. These are covered with a 3 to 10 mm thick layer of fine green muscovite crystals which look a dull olive green from some directions, but a sparkly light metallic green from others. Thre is a bit of a pink tinted calcite present. A loupe reveals that some of the small green crystals of muscovite are truly beautiful and transparent.
no photo
mus-28 ($ 48.00)
Ouro Fino Mine, Coronel Murta, Minas Gerais, Brazil
 

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