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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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