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Formula: C
Native element, isometric paramorph of
hexagonal, shock-metamorphosed
chaoite,
diamond formed at temperature 950oC or above and pressure
4.5 GPa or above,
hexagonal low pressure high temperature graphite,
isometric tartarosite found as inclusions in diamond
and
UM2003-04-E:C
Crystal System: Hexagonal
Specific gravity: 3.2 measured, 3.51 calculated
Hardness: 7 to 8
Colour: Transparent brownish yellow, greyish
Environments
Plutonic igneous environments
Meteorites
Localities
At the Allan Hills A77283 meteorite, Allan Hills, Victoria Land, Eastern Antarctica, Antarctica, lonsdaleite
is associated with troilite,
graphite, diamond,
schreibersite and cohenite
(HOM).
The Goalpara meteorite, Goalpara District, Assam, India, is a
stony ureilite meteorite where lonsdaleite and
diamond formed directly from
graphite through buckling and puckering of hexagonal carbon planes of
graphite. The shock origin of
diamond in
ureilites is confirmed
(AM 56.333–336).
At the Popigai impact crater, Taymyrsky Dolgano-Nenetsky District, Krasnoyarsk Krai, Russia, several coexisting
carbon phases forming tight aggregates have been found, including cubic and hexagonal
diamond paramorphs,
graphite, amorphous carbon and onion-like carbon. The latter is described
within impact diamonds for the first time
(EJM 26.267–277).
At the type locality, the Canyon Diablo meteorite, Meteor Crater area, Coconino County, Arizona, USA,
lonsdaleite was discovered in the residue (~200 mg) from the dissolution of 5 kg of the
meteorite. The lonsdaleite may be formed by impact
shock, or be a product of direct crystallisation in the parent body. Associated minerals include
schreibersite, cohenite,
taenite, graphite,
chromite, kosmochlor,
sphalerite and carbonado
(HOM).
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