Chaoite

chaoite

diamond

tartarosite

zircon

Images

Formula: C
Native element, hexagonal paramorph of
isometric diamond formed at temperature 950oC or above and pressure 4.5 GPa or above,
hexagonal low pressure high temperature graphite,
hexagonal lonsdaleite formed by shock-compression of graphite,
isometric tartarosite found as inclusions in diamond
and UM2003-04-E:C
Crystal System: Hexagonal
Specific gravity: 3.43 calculated
Hardness: 1 to 2
Colour: Black
Common impurities: Si,Cl
Environments

Metamorphic environments
Meteorites

Chaoite occurs in shock-metamorphosed graphite gneisses and meteorites. Associated minerals include graphite, zircon, rutile, pseudobrookite, magnetite, nickel-bearing pyrrhotite and baddeleyite (HOM).

Localities

At the Lappajärvi meteorite crater, Lappajärvi, South Ostrobothnia, Finland, impact diamond paramorphs derived from target graphite have been found in suevites. They exist as cubic crystals with fine polycrystalline textures and a preferred orientation of crystallites. The grains involve accessory phases of chaoite and graphite. The diamonds discovered are mineralogical indicators of shock metamorphism under pressures from 60 to 140 kilobar (Russian Geology and Geophysics 40.1487–1490).

At the type Locality, Möttingen, Donau-Ries District, Swabia, Bavaria, Germany, chaoite occurs as thin lamellae (3 to 15 microns wide), alternating with graphite. The chaoite was recovered from shocked graphite gneisses by treatment with HF. The insoluble residue included chaoite, graphite, zircon and rutile. Chaoite was found only in specimens in which the silicates were fused to glass (AM 54.326-330 as an unnamed polymorph of carbon).
Chaoite from Möttingen - Image

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