Ice Ic (pronounced "ice one c") is a metastablecubiccrystalline variant of ice. The oxygen atoms are arranged in a diamond structure. It is produced at temperatures between 130 and 220 K (−140 and −50 °C), and can exist up to 240 K, when it transforms into ice Ih. It may occasionally be present in the upper atmosphere.
Ordinary water ice is known as ice Ih, (in the Bridgman nomenclature). Different types of ice, from ice II to ice XV, have been created in the laboratory at different temperatures and pressures.