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Lars & List
The important point is that most hor desert
meteorites are not found in sandy areas ( like sans dunes) but in hard areas
such as rocky fields, with most of the time clay below ( or finer soils than
sand below the surface) ( The Dar Al Gani field is made of small
dolomitic rocks ( a kind of calcareous rock) lying on clay. Most of
the saharan Hamadas are similar. These soils keep the moisture
when it rains and this is the cause of the weathering of the buried "half" of
the meteorite. The upper part of the meteorite is in very dry atmosphere and
keeps it in better state of conservation. Even if the crust is somehow blasted
away by the sand wind action.
A typical old hot desert meteorite will present: no
crust on the upper side, and some crust , but altered on the buried side,
sometimes this crust will be covered with caliche.
Desert sand is not chemicaly agressive. Desert sand
is almost pure silica ( Si O2). the color of the sand is given by oxydes in very
small proportions. Often iron oxydes. Aggresion ( and alteration ) on hot
desert meteorites occurs when water is present. The fusion crust is not a
propection for meteorites. It is not a sealant. Unfortunatly.
I only speak about stones meteorites ( Chondrites
and Achondrites ) I have no experience about iron meteorites, just
found one.
My 2 cents
Michel FRANCO
Hot desert hunter.
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