Thaumasite
Ca₃(SO₄)(CO₃){Si(OH)₆} · 12H₂O

     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; P6₃.
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/cm³.
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:

REFERENCES:
MinRec 21:342 (1990), Dana 8:671 (1997)

DISTRIBUTION AND RARITY AT MONT SAINT-HILAIRE:

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