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Montmorillonite crystals
© David Joyce
(Na,Ca0.50.33(Al,Mg)Si10(OH) · nH
Montmorillonite, a member of the smectite group, is very rare at Mont Saint-Hilaire.
PHYSICAL CHARACTERISTICS:
Color is usually white to tan.
Luster is earthy.
Diaphaneity is transparent to translucent.
Crystal System is monoclinic; 2/
Crystal Habits include compact powdery fillings.
Cleavage {001} is perfect (not seen in powdery material).
Fracture is absent due to clay-like nature.
Hardness is 1 -2.
Specific Gravity is approximately 2.7 g/cm
Streak is white.
Associated Minerals include albite and fluorite.
Distinguishing Features: none amongst other powdery material.
Origin: Named in 1847 after its discovery locality, at Montmorillon,
northwest of Limoges, France.
CLASSIFICATION:
Dana System
# 71.3.1a.2
Strunz Classification
# VIII/H.19-20
REFERENCES:
MinRec 21:323 (1990), Dana 8:1483-1485 (1997)
DISTRIBUTION AND RARITY AT MONT SAINT-HILAIRE:
MSH
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