[meteorite-list] Carbonados

[bernd.pauli at paulinet.de]

Elton wrote: "As far as I know the diamonds are only found in rim recoveries."

Hello Elton, Marcin, and List,

Nininger was the one who first observed that diamonds were only found in fragments
recovered from the rim. All these meteorites had a reheated, granulated matrix. Nininger
suggested that the temperatures indicated were those required to form diamonds from
graphite during the passage of shock waves produced in the meteorite upon collision
with the Earth.

Most carbonados are about 0.1-1.0 mm (some up to 2.2 mm) in diameter, a little porous,
layered and polycrystalline. They usually occur in amorphous carbon-graphite-troilite nodules.

Many of the carbonados are aggregates of diamond and a hexagonal polymorph of diamond
called lonsdaleite.

Reference:

BUCHWALD V.F. (1975) Handbook of Iron Meteorites (Volume 2, Canyon Diablo, pp. 384-385).


Best wishes,

Bernd