Muscovite

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Muscovite crystals - click for larger pic
Muscovite crystals
© Doug Merson

KAl(SiAl)O10(OH,F)11

Muscovite, a member of the mica group, is uncommon at MSH. It is hard to distinguish from the other members of the mica group.

PHYSICAL CHARACTERISTICS:

Color ranges from pale yellow to pale green, colorless and light brown.
Luster is vitreous to pearly.
Diaphaneity is transparent to translucent.
Crystal System is monoclinic; 2/
Crystal Habits include small plates and short pseudohexagonal prisms,
intergrown clusters, globular aggregates and embedded masses.
Cleavage {001} is perfect.
Fracture is not apparent due to cleavage.
Hardness is 2.5 – 3.5
Specific Gravity is approximately 2.8 g/cm
Streak is white.
Associated Minerals include albite, anatase, ancylite, beryl, calcite,
chlorite group, dolomite, magnesite, marcasite, pyrite, pyrrhotite,
quartz, siderite and UK # 56.
Distinguishing Features: Crystal habit.
Origin: Named in 1850 and is derived from its use in windows as
muscovy glass, Muscovy being an old Russian Province.

CLASSIFICATION:

Dana System
# 71.2.2a.1

Strunz Classification
# VIII/H.10-30

REFERENCES:
MinRec 21:324 (1990), Dana 8:1448-1451 (1997)

DISTRIBUTION AND RARITY AT MONT SAINT-HILAIRE:

MSH
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