Cu(SO)(OH) · 2H
Posnjakite occurs rarely at Mont Saint-Hilaire.
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/cm
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),
Dana 8:643 (1997)
DISTRIBUTION AND RARITY AT MONT SAINT-HILAIRE: