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Formula: Ca(CO3)
Anhydrous normal carbonate, hexagonal paramorph of orthorhombic
aragonite and trigonal calcite,
forms a series with bastnäsite
Crystal System: Hexagonal
Specific gravity: 2.645 measured and calculated
Hardness: 3
Streak: White
Colour: Colourless
Environments
Metamorphic environments
Hydrothermal environments
Vaterite is a rare form of CaCO3 that is metastable below about 400°C. Dry crystals are stable in air
but convert to calcite when heated to about 440°C. Converts to
aragonite or calcite when boiled in
water. Converts to calcite when boiled in NaCl solution (Mindat). It is a
major constituent of a carbonated calcium silicate hydrogel complex formed from
larnite
(Webmin).
Localities
At the Sulu ultrahigh-pressure metamorphic belt, Shandong, China, vaterite was identified in a decrepitated
(disintegrated when heated) carbonaceous material-bearing inclusion in zircon
from a migmatite. It is associated with nanometer to micrometer sized
anhedral diamonds, aragonite,
calcite and other amorphous materials.
Indications are that an amorphous calcium carbonate phase occurred as the precursor of vaterite. Decrepitation
of the inclusion resulted in an extremely high supersaturation state of the fluid that induced the precipitation of
amorphous materials and released residual fluid out of the inclusion, which became dry and preserved
vaterite and amorphous materials.
(AM 107.1410-1424).
At the Hatrurim Formation, Tamar Regional Council, Southern District, Israel, vaterite is a rock-forming mineral
formed at low temperatures by hydration of metamorphic calc-silicate rocks in the presence of atmospheric carbon dioxide,
in slightly metamorphosed marl and
conglomerate, and in weathering crusts. Associated minerals include
calcite, aragonite,
tobermorite,
grossular-katoite and
kaolinite
(HOM).
At Ballycraigy, Larne, County Antrim, Northern Ireland, UK, vaterite is a major constituent of a carbonated
calcium silicate hydrogel complex formed from larnite (HOM) and also as
paramorphs after larnite
(Dana).
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