Coesite

High-pressure polymorph of silicon dioxide (SiO2). Has the same chemical composition as cristobalite, stishovite, seifertite and tridymite but possesses a different crystal structure. Coesite forms at intense pressures of above about 2.5 GPa (25 kbar) and temperature above about 700 °C, and was first found naturally on Earth in impact craters. More recently, coesite and other high pressure silica polymorphs have been found in lunar specimens (sample return and meteorites) and eucrites.