Name/Title
MuscoviteEntry/Object ID
2009.62.114Description
Chemical Composition: KAl2(ASi3O10)(F,OH)2
Crystal System: Monoclinic System
Description: Common Name: Muscovite
Chemistry: KAl2(AlSi3O10)(F, OH)2, Potassium aluminum silicate hydroxide fluoride.
Group: Micas
Location: Minas Gerais, Brazil
Description: Thin translucent plates uniform in thickness,amber to a light silver in appearance.
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.
Best Field Indicators are crystal habit, cleavage, elastic sheets, color and associations.
Fracture: uneven
Hardness: 2 Gypsum
Luster: Vitreous
Occurrence: Muscovite is the most common mica, found in granites, pegmatites, gneisses, and schists, and as a contact metamorphic rock or as a secondary mineral resulting from the alteration of topaz, feldspar, kyanite, etc. In pegmatites, it is often found in immense sheets that are commercially valuable. Muscovite is in demand for the manufacture of fireproofing and insulating materials and to some extent as a lubricant
Specific Gravity: 2.8
Streak: white
Variety: 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.Collection
RAGM Mineral CollectionDimensions
Width
5-1/4 inDepth
1/2 inLength
5 inWeight
0.66 ozLocation
Location
Display Case
FS-4Room
Frieda Smith HallBuilding
Crater Rock MuseumCategory
PermanentDate
August 17, 2023