Magnesioarfvedsonite
Na₃(Mg,Fe²⁺)₄Fe³⁺Si₈O₂₂(OH)₂

     Magnesio-arfvedsonite, a member of the amphibole group, is very rare at MSH. It is almost identical to arfvedsonite in appearance and is indistinguishable visually.

PHYSICAL CHARACTERISTICS:

Color varies from blue-green to black.
Luster is vitreous to dull.
Diaphaneity is translucent to opaque.
Crystal System is monoclinic; C2/m.
Crystal Habits include prismatic crystals to 9cm and fine-
   grained matrix material.
Cleavage {110} is perfect.
Fracture is uneven to subconchoidal.
Hardness is 5 - 6.
Specific Gravity is approximately 3.3 g/cm³.
Streak is dark bluish-gray.
Associated Minerals include aegirine, albite, analcime, ancylite
   biotite, calcite, catapleiite, eudialyte, fluorite, microcline, narsarsukite,
   natrolite, petarasite, polylithionite, rhodochrosite and titanite. Distinguishing Features: Crystal habit and color.
Origin: Named in 1957 as the magnesium-dominant analog of
   arfvedsonite.

CLASSIFICATION:

REFERENCES:
MinRec 21:321 (1990), Dana 8:1364-1365 (1997)

DISTRIBUTION AND RARITY AT MONT SAINT-HILAIRE:

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