Oligoclase
NaAlSi₃O₈

     Oligoclase, a member of the feldspar group, is moderately rare at MSH.

PHYSICAL CHARACTERISTICS:

Color is usually dull green.
Luster is vitreous.
Diaphaneity is transparent to translucent.
Crystal System is triclinic; C1.
Crystal Habits include phenocrysts.
Cleavage {001} is perfect and {010} is good.
Fracture is conchoidal to uneven.
Hardness is 6 - 6.5
Specific Gravity is approximately 2.65 g/cm³.
Streak is white.
Associated Minerals include (??).
Distinguishing Features: Crystal habit.
Origin: Named in 1826 from the Greek oligos, small, plus klan, to break,
   because it was thought to have a less perfect cleavage than albite.

CLASSIFICATION:

REFERENCES:
Dana 8:1608-1614 (1997)

DISTRIBUTION AND RARITY AT MONT SAINT-HILAIRE:

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