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Annite crystals
© Doug Merson
KFe2+(AlSi10)(OH,F)
A member of the mica group, annite is indistinguishable from biotite and is uncommon at MSH.
PHYSICAL CHARACTERISTICS:
Color is usually black or dark green.
Luster is vitreous to submetallic.
Diaphaneity is transparent to opaque.
Crystal System is monoclinic; 2/
Crystal Habits include large well-formed pseudohexagonal prisms
to 12cm across and 15cm long.
Cleavage: {001} is perfect.
Fracture is uneven.
Hardness is 2 – 3.
Specific Gravity is approximately 3.3 g/cm
Streak is white.
Associated Minerals include microcline.
Distinguishing Features: Crystal habit and color.
Origin: Named in 1868 after its discovery locality at Cape Ann,
Essex county, Massachusetts, U.S.A..
CLASSIFICATION:
Dana System
# 71.2.2b.3
Strunz Classification
# VIII/H.11-50
REFERENCES:
MinRec 21:296 (1990), Dana 8:1461 (1997)
DISTRIBUTION AND RARITY AT MONT SAINT-HILAIRE:
MSH
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