[meteorite-list] Stones partly burried in the dessert sand

From: Michel Franco <michel_at_meteoritecentral.com>
Date: Thu Apr 22 10:32:57 2004
Message-ID: <000901c41762$6f71cf60$0201a8c0_at_cailloubi12zzr>

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Lars & List=20

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.=20

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.=20

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.=20

I only speak about stones meteorites ( Chondrites and Achondrites ) I =
have no experience about iron meteorites, just found one.=20

My 2 cents

Michel FRANCO
Hot desert hunter.=20

Caillou Noir www.caillou-noir.com
BP 16, 100 Chemin des Camp=E8nes
74400 Les Praz de Chamonix FRANCE
  ----- Original Message -----=20
  From: Lars Pedersen=20
  To: Meteorite Mailing List=20
  Sent: Wednesday, March 31, 2004 10:15 PM
  Subject: [meteorite-list] Stones partly burried in the dessert sand


  Hi All

  I have been thinking ;-)

  Why is it that it looks like the part of a meteorite that sticking out =
of the sand seems to be better preserved, than the part that is burried =
in the sand - and is protected from the weather.

  My logical sense (dont laugh :-) tells me that the part that is up in =
the air is constantly eroded by the sand blowing over it, and gently =
sandblasting it - but perhaps that is the secret ?

  Is dessert sand cemicaly agressive ?

  It is just something I noticed, and may not allways be the case ?

  Best wishes
  Lars Pedersen
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<BODY bgColor=3D#ffffff>
<DIV><FONT face=3DArial size=3D2>Lars &amp; List </FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2>The important point is that most hor =
desert=20
meteorites are not found in sandy areas ( like sans dunes) but in hard =
areas=20
such as rocky fields, with most of the time clay below ( or finer soils =
than=20
sand&nbsp;below the surface) ( The Dar Al Gani field is made of small=20
dolomitic&nbsp;rocks &nbsp;( a kind of calcareous rock) lying on clay. =
Most of=20
the saharan Hamadas&nbsp;are&nbsp;&nbsp;similar. These soils keep the =
moisture=20
when it rains and this is the cause of the weathering of the buried =
"half" of=20
the meteorite. The upper part of the meteorite is in very dry atmosphere =
and=20
keeps it in better state of conservation. Even if the crust is somehow =
blasted=20
away by the sand wind&nbsp;action. </FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2>A typical old hot desert meteorite will =
present: no=20
crust on the upper side, and some crust , but altered on the buried =
side,=20
sometimes this crust will be covered with caliche. </FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2>Desert sand is not chemicaly agressive. =
Desert sand=20
is almost pure silica ( Si O2). the color of the sand is given by oxydes =
in very=20
small proportions. Often iron oxydes. &nbsp;Aggresion ( and alteration ) =
on hot=20
desert meteorites occurs when water is present. The fusion crust is not =
a=20
propection for meteorites. It is not a sealant. Unfortunatly. =
</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2>I only speak about stones meteorites ( =
Chondrites=20
and Achondrites ) &nbsp;I have&nbsp;no experience about iron meteorites, =
just=20
found one. </FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2>My 2 cents</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2>Michel FRANCO</FONT></DIV>
<DIV><FONT face=3DArial size=3D2>Hot desert hunter. </FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2>Caillou Noir <A=20
href=3D"http://www.caillou-noir.com">www.caillou-noir.com</A><BR>BP 16, =
100 Chemin=20
des Camp=E8nes<BR>74400 Les Praz de Chamonix FRANCE</FONT></DIV>
<BLOCKQUOTE dir=3Dltr=20
style=3D"PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; =
BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
  <DIV style=3D"FONT: 10pt arial">----- Original Message ----- </DIV>
  <DIV=20
  style=3D"BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: =
black"><B>From:</B>=20
  <A title=3Dlbp_at_privat.tdcadsl.dk =
href=3D"mailto:lbp_at_privat.tdcadsl.dk">Lars=20
  Pedersen</A> </DIV>
  <DIV style=3D"FONT: 10pt arial"><B>To:</B> <A=20
  title=3Dmeteorite-list_at_meteoritecentral.com=20
  href=3D"mailto:meteorite-list_at_meteoritecentral.com">Meteorite Mailing =
List</A>=20
  </DIV>
  <DIV style=3D"FONT: 10pt arial"><B>Sent:</B> Wednesday, March 31, 2004 =
10:15=20
  PM</DIV>
  <DIV style=3D"FONT: 10pt arial"><B>Subject:</B> [meteorite-list] =
Stones partly=20
  burried in the dessert sand</DIV>
  <DIV><FONT face=3DArial size=3D2></FONT><BR></DIV>
  <DIV><FONT face=3DArial size=3D2>Hi All</FONT></DIV>
  <DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
  <DIV><FONT face=3DArial size=3D2>I have been thinking ;-)</FONT></DIV>
  <DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
  <DIV><FONT face=3DArial size=3D2>Why is it that it looks like the part =
of a=20
  meteorite that sticking out of the sand seems to be better preserved, =
than the=20
  part that is burried in the sand - and is protected from the=20
  weather.</FONT></DIV>
  <DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
  <DIV><FONT face=3DArial size=3D2>My logical sense (dont laugh :-) =
tells me that=20
  the part that is up in the air is constantly eroded by the sand =
blowing over=20
  it, and gently sandblasting it - but perhaps that is the secret =
?</FONT></DIV>
  <DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
  <DIV><FONT face=3DArial size=3D2>Is dessert sand cemicaly agressive =
?</FONT></DIV>
  <DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
  <DIV><FONT face=3DArial size=3D2>It is just something I noticed, and =
may not=20
  allways be the case ?</FONT></DIV>
  <DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
  <DIV><FONT face=3DArial size=3D2>Best wishes</FONT></DIV>
  <DIV><FONT face=3DArial size=3D2>Lars=20
Pedersen</FONT></DIV></BLOCKQUOTE></BODY></HTML>

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Received on Wed 31 Mar 2004 03:55:01 PM PST


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