Ice III

Ice III is a form of solid matter which consists of tetragonal crystalline ice, formed by cooling water down to 250 K at 300 MPa. It is the least dense of the high-pressure water phases, with a density of 1160 kg/m³ (at 350 MPa). The proton-ordered form of ice III is ice IX.

Ordinary water ice is known as ice I_h, (in the Bridgman nomenclature). Different types of ice, from ice II to ice XVI, have been created in the laboratory at different temperatures and pressures.