[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> This is a multi-part message in MIME format. ------=_NextPart_000_0006_01C41773.32AC0A30 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable 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 ------=_NextPart_000_0006_01C41773.32AC0A30 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML><HEAD> <META http-equiv=3DContent-Type content=3D"text/html; = charset=3Diso-8859-1"> <META content=3D"MSHTML 6.00.2800.1400" name=3DGENERATOR> <STYLE></STYLE> </HEAD> <BODY bgColor=3D#ffffff> <DIV><FONT face=3DArial size=3D2>Lars & List </FONT></DIV> <DIV><FONT face=3DArial size=3D2></FONT> </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 below the surface) ( The Dar Al Gani field is made of small=20 dolomitic rocks ( a kind of calcareous rock) lying on clay. = Most of=20 the saharan Hamadas are 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 action. </FONT></DIV> <DIV><FONT face=3DArial size=3D2></FONT> </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> </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. 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> </DIV> <DIV><FONT face=3DArial size=3D2>I only speak about stones meteorites ( = Chondrites=20 and Achondrites ) I have no experience about iron meteorites, = just=20 found one. </FONT></DIV> <DIV><FONT face=3DArial size=3D2></FONT> </DIV> <DIV><FONT face=3DArial size=3D2>My 2 cents</FONT></DIV> <DIV><FONT face=3DArial size=3D2></FONT> </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> </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> </DIV> <DIV><FONT face=3DArial size=3D2>I have been thinking ;-)</FONT></DIV> <DIV><FONT face=3DArial size=3D2></FONT> </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> </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> </DIV> <DIV><FONT face=3DArial size=3D2>Is dessert sand cemicaly agressive = ?</FONT></DIV> <DIV><FONT face=3DArial size=3D2></FONT> </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> </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> ------=_NextPart_000_0006_01C41773.32AC0A30-- Received on Wed 31 Mar 2004 03:55:01 PM PST |
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