Posnjakite
Cu₄(SO₄)(OH)₆ · 2H₂O

     Posnjakite occurs rarely at Mont Saint-Hilaire.

PHYSICAL CHARACTERISTICS:

Color is usually greenish-blue.
Luster is vitreous.
Diaphaneity is transparent to translucent.
Crystal System is monoclinic; Pc.
Crystal Habits include efflorescences.
Cleavage is perfect.
Fracture is uneven.
Hardness is 2 - 3.
Specific Gravity is approximately 3.3 g/cm³.
Streak is bluish.
Associated Minerals include UK #55.
Distinguishing Features: Crystal habit, color and streak.
Origin: Named in 1967 after Eugene Waldemar Posnjak (1888-1949),
   American geochemist.

CLASSIFICATION:

REFERENCES:
Dana 8:643 (1997)

DISTRIBUTION AND RARITY AT MONT SAINT-HILAIRE:

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