page_title: Ikaite
section_title: Structure
hierarchical_section_title: Ikaite / Structure
caption_attribution_description: English: Structure of Ikaite.
context_page_description: Ikaite is the mineral name for the hexahydrate of calcium carbonate, CaCO₃·6H₂O. Ikaite tends to form very steep or spiky pyramidal crystals, often radially arranged, of varied sizes from thumbnail size aggregates to gigantic salient spurs. It is only found in a metastable state and decomposes rapidly by losing most of its water content once removed from near-freezing water. This "melting mineral" is more commonly known through its pseudomorphs.
context_section_description: Ikaite crystallizes in the monoclinic crystal system in space group C2/c with lattice parameters a~8.87A, b~8.23A, c~11.02A, β~110.2°. The structure of ikaite consists of an ion pair of (Ca²⁺CO₃²⁻)⁰ surrounded by a cage of hydrogen-bonded water molecules which serve to isolate one ion pair from another.
caption: Ion pair (Ca2+CO32−)0 and hydration cage. Part of the crystal structure of ikaite. Ca (blue) is in dodecahedral coordination with O atoms (red) of the carbonate (black planar) and water molecules, while hydrogen bonds (dotted) between H-atoms (yellow) of the water molecules to the O-atoms of the carbonate ion exist.[14][16]
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