[meteorite-list] RE: Crust and Meteorite Thin Sections
From: MARK BOSTICK <thebigcollector_at_meteoritecentral.com>
Date: Thu Apr 22 10:31:15 2004 Message-ID: <BAY4-DAV29Fs0OfBEcD00012104_at_hotmail.com> ------=_NextPart_001_0035_01C42531.E0D2C0B0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Hello Jeff and list, I have not seen anyone answer your question so I will give my thoughts. "If you found a basaltic rock with a thin black rind in the desert and th= e rind looked translucent red and isotropic in thin section, would you say = "I got a meteorite" or "My, what an interesting caliche"? What other ways of differentiating rind from crust are there?" I would not use "a thin black rind in the desert" stones as an identifica= tion marker for meteorites. I would be much more interested in what the = stone looks like inside. If the stone looked suspicious, and I could not= identify the stone in the field, I would take the coordinates of the fin= d, make small field notes and save it to look at it later. So I would ju= st think "Interesting". The problem with using fusion crust as an identification marker is that c= rust is not consistent. I have several stones I can show you with multip= le histories of breaking up, each section with a different degree of fusi= on crust. So if you were looking at a thin section and only noticed "tra= nslucent red and isotropic" in the crust, it would not tell me anything a= nd I would be much more interested in seeing the matrix of the meteorite.= The achondrites would be harder to identify for the field collector, an= d sine you mentioned "basaltic rock" I will assume that is what you are r= eferring to, So I would be wondering, when viewing the thin section, How= big are the crystals in the matrix, do you see typical twinning, any sig= ns of shock minerals, do you see any olivine and how is it formed, and ho= w much of the matrix is fined grained? These are things I am looking at = in an achondrite meteorite. I am sure others could add other notes. The thin sections I have that show crust of a meteorite, usually show it = as black if the meteorite is fresh, you will see a few spots of color mix= ed in the crust line. I have never compared the thin section crust of a = desert vanished meteorite, (or paid much attention in general to the weat= hered crust) that I have on thin sections, with that of a fresh fall but = if there is enough interest, I could take a few photographs and share the= m. (Nice thin section photos are not the easiest thing for me to make). Mark Bostick, (often spelled by list members as Bostock, Bostik, or Bosti= c, and I will answer to all of them..:-) www.meteoritearticles.com ------=_NextPart_001_0035_01C42531.E0D2C0B0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable <HTML><BODY STYLE=3D"font:10pt verdana; border:none;"><DIV>Hello Jeff and= list,</DIV> <DIV> </DIV> <DIV>I have not seen anyone answer your qu= estion so I will give my thoughts.</DIV> <DIV><BR>"If you found a basalti= c rock with a thin black rind in the desert and the<BR>rind looked transl= ucent red and isotropic in thin section, would you say "I<BR>got a meteor= ite" or "My, what an interesting caliche"?<BR>What other ways of differen= tiating rind from crust are there?"</DIV> <DIV> </DIV> <DIV>I would = not use "a thin black rind in the desert" stones as an identification mar= ker for meteorites. I would be much more interested in what the sto= ne looks like inside. If the stone looked suspicious, and I could n= ot identify the stone in the field, I would take the coordinates of the f= ind, make small field notes and save it to look at it later. So I w= ould just think "Interesting".</DIV> <DIV> </DIV> <DIV>The problem w= ith using fusion crust as an identification marker is that crust is not c= onsistent. I have several stones I can show you with multiple histo= ries of breaking up, each section with a different degree of fusion crust= So if you were looking at a thin section and only noticed "transl= ucent red and isotropic" in the crust, it would not tell me anything and = I would be much more interested in seeing the matrix of the meteorite.&nb= sp; The achondrites would be harder to identify for the field collector, = and sine you mentioned "basaltic rock" I will assume that is what you are= referring to, So I would be wondering, when viewing the thin secti= on, How big are the crystals in the matrix, do you see typical twinning, = any signs of shock minerals, do you see any olivine and how is it formed,= and how much of the matrix is fined grained? These are things I am= looking at in an achondrite meteorite. I am sure others could add = other notes.</DIV> <DIV> </DIV> <DIV>The thin sections I have that s= how crust of a meteorite, usually show it as black if the meteorite is fr= esh, you will see a few spots of color mixed in the crust line. I h= ave never compared the thin section crust of a desert vanished meteorite,= (or paid much attention in general to the weathered crust) that I have o= n thin sections, with that of a fresh fall but if there is enough in= terest, I could take a few photographs and share them. (Nice thin s= ection photos are not the easiest thing for me to make).</DIV> <DIV> = ;</DIV> <DIV>Mark Bostick, (often spelled by list members as Bostock, Bos= tik, or Bostic, and I will answer to all of them..:-)</DIV> <DIV><A href=3D= "http://www.meteoritearticles.com">www.meteoritearticles.com</A></DIV> <D= IV> </DIV> <DIV><BR> </DIV></BODY></HTML> ------=_NextPart_001_0035_01C42531.E0D2C0B0-- Received on Sun 18 Apr 2004 11:42:42 AM PDT |
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