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Thomsonite-Ca crystals - click for larger pic
Thomsonite-Ca crystals
Scheerine specimen
Photo by Violet Anderson
© Royal Ontario Museum

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Thomsonite-Ca
(Ca,Sr)2NaAl5Si5O20 · 6H2O

     Thomsonite-Ca is a very rare zeolite at Mont Saint-Hilaire.

PHYSICAL CHARACTERISTICS:

Color is usually colorless or white.
Luster is vitreous to dull.
Diaphaneity is transparent to translucent.
Crystal System is orthorhombic; Pcnn.
Crystal Habits include fibrous crystals to 2mm and spherical
   aggregates to 8mm.
Cleavage {010} is perfect and {100} is distinct.
Fracture is uneven to subconchoidal.
Hardness is 5 - 5.5
Specific Gravity is approximately 2.3 g/cm3.
Streak is white.
Associated Minerals include aegirine, albite, analcime, apophyllite
   series, calcite, catapleiite, donnayite, fluorite, natrolite, pectolite,
   pyrophanite and sérandite.
Distinguishing Features: none from other white fibrous species.
Origin: Named in 1820 for Thomas Thomson (1773-1852), Scottish
   chemistry professor who analyzed the mineral.

CLASSIFICATION:

Dana System
# 77.1.5.9

Strunz Classification
# VIII/J.21-70

REFERENCES:
MinRec 21:342 (1990), Dana 8:1687-1688 (1997)

DISTRIBUTION AND RARITY AT MONT SAINT-HILAIRE:

MSH
¤¤¤

PE
--

AP
--

MX
--

SS
--

MC
¤¤

HF
--

BR
¤¤

SX
--

FR
--

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