Magnesiohornblende
Ca₂(Mg,Fe²⁺)₄Al{AlSi₇O₂₂}(OH)₂

     (Alumino)magnesiohornblende, a member of the amphibole group, is uncommon at MSH. Though it easy to determine that it is an amphibole, it is very difficult to distinguish from other amphiboles.

PHYSICAL CHARACTERISTICS:

Color is usually greenish brown or black.
Luster is vitreous.
Diaphaneity is translucent.
Crystal System is monoclinic; C2/m.
Crystal Habits include black prisms to several millimeters.
Cleavage {110} is perfect.
Fracture is uneven to subconchoidal.
Hardness is 5 - 6.
Specific Gravity is approximately 3.2 g/cm³.
Streak is grayish-green.
Associated Minerals include amphibole group, analcime, biotite
   and pyrite.
Distinguishing Features: Crystal habit.
Origin: Named for its composition, it is the magnesium-dominant
   end-member of the hornblende group of calcic amphiboles.

CLASSIFICATION:

REFERENCES:
MinRec 21:315 (1990), Dana 8:1350-1352 (1997)

DISTRIBUTION AND RARITY AT MONT SAINT-HILAIRE:

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