Calcite after Ikaite var. Glendonite concretion. — Photo: Mbz1 · CC Attribution-Share Alike 3.0 Unported, 2.5 Generic, 2.0 Generic and 1.0 Generic license
Ikaite
Calcium carbonate hexahydrate — the cold-water 'melting mineral' that grows spiky crystals in near-freezing springs and sea floors.
Intro adapted from Wikipedia (CC BY-SA).
Ikaite is an IMA-recognized mineral species in the carbonate class, with the chemical formula Ca(CO₃)·6H₂O.
It crystallizes in the monoclinic crystal system (space group C2/c).
Key properties: Mohs hardness 3; specific gravity 1.77; refractive index 1.513; optically biaxial.
IMA symbol Ika, IMA status: approved, named in 1962.
Forms in sea water and lake water in anerobic, organic-rich periglacial and glaciomarine environments near 0 ° C, readily converting to calcite at higher temperatures.
The name refers to the Ika Fjord, Greenland, where the first specimens were collected.