Hand Specimen identification: Coesite cannot be identified in hand specimen.
Chemical Composition : SiO2
Hardness : 7 to 8
Cleavage/Fracture : none/conchoidal
Luster/Transparency : vitreous/transparent
Color : colorless
Streak : white
Optical Properties : Biaxial 1+ 2, a = 1.59, b = 1.60, g = 1.60,d = 0.01, 2V = 64°.
Crystallography : Monoclinic, a = 7.17, b = 12.33, c = 7.17, b = 120.0°,
Z = 16; space group C2/c; point group 2/m.
Habit : Crystals are usually thin tabs, invisible without a microscope.
Structure and composition : Coesites structure consists of a very dense three-dimensional network of SiO4 tetrahedra. In some ways, the structure is similar to that of feldspars.
Occurrence and associations : Coesite, a rare high-pressure polymorph of SiO2, is known only from meteor impact craters and some rare xenoliths and other rocks of deep crust or man-tle origin
Related Minerals : SiO2 polymorphs include quartz, cristobalite, tridymite, coesite, and stishovite.