Ikaite

minerals

calcite

pseudomorph

opal

Images
Formula: Ca(CO₃).6H₂O
Hydrated normal carbonate
Specific gravity: 1.77 to 1.8
Streak: White
Colour: Chalky white
Environments

Hydrothermal environments

Ikaite is a very rare carbonate that forms in sea water and lake water in anaerobic (oxygen deficient), organic-rich periglacial (subject to repeated freezing and thawing) and glaciomarine (containing both glacial ice and marine water) environments near 0^oC, readily converting to calcite at higher temperatures of about 8^oC (HOM, Mindat, Webmin).

Localities

At White Cliffs, New South Wales, Australia, opal pseudomorphs after ikaite have been found (KL p259).

At the type locality, Ikka Bund, Ikka Fjord, Sermersooq, Greenland, Denmark, chalklike underwater pillars of ikaite occur in the inner part of the fjord, 8 km south of Ivigtut. The pillars reach to within half a metre of the water surface. The temperature at the base of the pillars was 3^oC and 7^o at the top. Samples were collected by a frogman and shipped in a refrigerator at about 4^oC (AM 49.439).

At the Olitsna river, White Sea coast, Karelia Republic, Russia, calcite pseudomorphs after ikaite have been found (KL p154). These pseudomorphs are sometimes called "glendonite" (Mindat).

At Bielo More, Kola Peninsula, Murmansk Oblast, Russia, pseudomorphs of calcite after ikaite to 10 cm have been found (Extra Lapis English-4 p23).

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