© Bill Lechner
SiO · nH
Opal is extremely rare at Mont Saint-Hilaire.
Color is usually colorless or white.
Luster is vitreous to dull, waxy or greasy.
Diaphaneity is transparent to opaque.
Crystal System is amorphous.
Crystal Habits include (??).
Cleavage is absent.
Fracture is conchoidal, uneven, irregular to splintery.
Hardness is 5.5 – 6.5
Specific Gravity is approximately 2.1 g/cm
Streak is white.
Associated Minerals include (??).
Distinguishing Features: Crystal habit.
Origin: Known from Antiquity and named from the Greek opalios
or Sanskrit, upala, opal.
Dana 8:1587-1592 (1997)
DISTRIBUTION AND RARITY AT MONT SAINT-HILAIRE: