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Spray of thaumasite crystals
László Horváth specimen
Photo by Violet Anderson
© Royal Ontario Museum
Thaumasite crystals
© Doug Merson
Ca(SO)(CO){Si(OH)} · 12H
Thaumasite is rare at MSH.
PHYSICAL CHARACTERISTICS:
Color is usually colorless or white.
Luster is vitreous to silky and dull.
Diaphaneity is transparent to translucent.
Crystal System is hexagonal;
Crystal Habits include radiating aggregates of acicular crystals
to 5mm and matted masses.
Cleavage {101} is poor.
Fracture is subconchoidal.
Hardness is 3.5
Specific Gravity is approximately 1.88 g/cm
Streak is white.
Associated Minerals include aegirine, ancylite, apophyllite series,
astrophyllite, bastnäsite, calcite, catapleiite, fluorite, microcline,
pectolite, rhodochrosite and siderite.
Distinguishing Features: Crystal habit.
Origin: Named in 1878 from the Greek thaumazein, to be surprised,
alluding to its unusual composition.
CLASSIFICATION:
Dana System
# 32.4.4.4
Strunz Classification
# VIII/B.22-90
REFERENCES:
MinRec 21:342 (1990), Dana 8:671 (1997)
DISTRIBUTION AND RARITY AT MONT SAINT-HILAIRE:
MSH
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