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Silicates·Tectosilicates·Silica Group·Monoclinic

Coesite

SiO2

Hardness
7.5–8
Streak
White
Spec. Gravity
3.0
System
Monoclinic

About

Coesite is a very rare mineral that forms in unique ultra high metamorphism usually as a result of meteorite impacts. It was named after American chemist Loring Coes, Jr. (1915-1978), who first synthesized Coesite in 1953 before it was naturally discovered in Barringer Crater in 1960.
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Crystal Forms & Aggregates

Occurs only in microscopic prismatic and tabular crystals. It is usually as a white dust or glassy material around Quartz sand pebbles. A synthetic form has been produced with large crystals resembling those of Gypsum.

Click here for a detailed explanation on the crystal structure of Coesite and other forms of silica.

Striking Features

Occurrence, hardness

Environment

Found at crater sites from the impact of a meteorite, where it forms under extreme heat and pressure, and in ultra-high-pressure eclogite rocks.

Polymorphs

Noteworthy Localities

Natural Coesite has been reported in the Barringer Crater (also known as Meteor Crater) in Coconino Co., Arizona; Sinking Springs Crater, Ohio; the Kentland Crater, Newton Co., Indiana; the Riess-kessel Crater, Bavaria, Germany; Kimberly, South Africa; and the Dora Maira Massif, Piedmont, Italy.

Common Mineral Associations

Photos

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