Origin of Name
Named after L. Coes, who first described it in detail.
Hand Specimen Identification
Coeste cannot be identified in hand specimen.
Coesite
Physical Properties
| Hardness | 6 to 7 |
| Specific Gravity | 2.28 |
| luster/transparency | vitreous/transparent to translucent |
| Color | colourless |
| streak | white |
| Fracture | Conchoidal |
| Cleavage | Absent |
Optical Properties
Biaxal (+), alpha=1.59, Beta=12.33, gamma=1.60, delta= 0.01, 2V= 64⁰
3D Structure
Crystallography
Monoclinic, a = 7.17, b = 12.33, c=7.17, beta= 120.0⁰, Z= 16, space group C2/c; point group 2/m.
You Might Like- Quartz mineral - physical and Optical Properties
- Cristobalite Mineral - Physical and Optical Properties
- Tridymite (low tridymite) SiO2, Physical and Chemical Properties
Habit
crystal are usually thin tabs, invisible without a microscope.
Structure and Composition
Coesite’s 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 f deep crust or mantle origin.
Related Minerals
SiO2 polymorphs include quartz, cristobalite, tridymite, coesite, and stishovite.