Gonnardite
(Na,Ca)_12-15(Al,Si)₄₀O₈₀ · nH₂O

     Tetranatrolite is now discredited. At Mont Saint-Hilaire it is actually gonnardite. This is a photo of the first MSH specimen that I acquired.

PHYSICAL CHARACTERISTICS:

Color is white.
Luster is silky to dull.
Diaphaneity is mostly opaque and rarely translucent.
Crystal System is tetragonal; I42d.
Crystal Habits include smalll prisms, fibrous sprays and coatings
   on natrolite.
Cleavage: none observed.
Fracture is (??).
Hardness is 5.
Specific Gravity is approximately 2.3 g/cm³.
Streak is white.
Associated Minerals include aegirine, amphibole group, analcime,
   ancylite-(Ce), microcline, montereginaite-(Y), narsarsukite and
   natrolite.
Distinguishing Features: Epitactic relationship with natrolite.
Origin: Named in 1896 for Ferdinand Gonnard, French mineralogist,
   who described gonnardite in 1871 as "mesole".

CLASSIFICATION:

REFERENCES:
MinRec 21:342 (1990), Dana 8:1685-1686 (1997)

DISTRIBUTION AND RARITY AT MONT SAINT-HILAIRE:

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