[meteorite-list] Color of OC's by Staining or by Trace Elements

From: cdtucson at cox.net <*cdtucson_at_meteoritecentral.com*> Date: Thu, 31 Mar 2011 17:30:42 -0400 Message-ID: <20110331173042.45W9H.282342.imail_at_fed1rmwml34> · cdtucson_at_meteoritecentral.com

--
Carl or Debbie Esparza
Meteoritemax
---- Laurence Garvie <lgarvie at asu.edu> wrote: 
> Just a quick reply to this subject as it could become lengthy and involved.
> 
> The primary coloring agent in meteorites is Fe2+ for fresh meteorites and Fe3+ for weathered ones (BTW - shocked meteorites can be black - see below). There is also Fe0, which is in the metal. 
> 
> When a few percent of Fe2+ is present, then minerals such as pyroxenes and olivines are usually green to greenish-yellow. A good example of Fe2+ coloring is in Johnstown, which is composed primarily of green pyroxene. 
> 
> If very little Fe2+ is present then pyroxene is normally white/clear as in the aubrites, such as Bishopville. 
> 
> In our oxidizing atmosphere, the metals in meteorites rust, producing Fe3+ -bearing oxides/oxyhydroxides. These rust minerals stain the meteorite and can range in color from yellow-orange-red-purple-brown-black.
> 
> Shocked meteorites can be black. A great comparison is between the two know chassignites - Chassigny and NWA2737, both of which have similar mineralogies. Fresh Chassigny is yellowish green - the color is caused by Fe2+ in the olivine. Yet, NWA2737 is black. The black color is caused by abundant 5 to 15 nanometer-sized iron-nickel droplets in the olivine, which are strongly absorbing in the visible and near-IR region of the spectrum. These droplets are formed during intense shock events.
> 
> Practically everything you ever wanted to know about color in minerals can be found at Prof. Rossman's site at http://minerals.gps.caltech.edu/
> 
> 
> Laurence
> CMS
> ASU
> 
> On Mar 30, 2011, at 7:52 PM, meteorite-list-request at meteoritecentral.com wrote:
> 
> > essage: 3
> > Date: Wed, 30 Mar 2011 12:20:31 -0400
> > From: Michael Gilmer <meteoritemike at gmail.com>
> > Subject: Re: [meteorite-list] Color of OC's by Staining or by Trace
> > 	Elements
> > To: Thunder Stone <stanleygregr at hotmail.com>
> > Cc: meteorite-list at meteoritecentral.com
> > Message-ID:
> > 	<AANLkTin9FfUsroBhMrVFDfH1_GCoss3B3L-vFf9zJ6T_ at mail.gmail.com>
> > Content-Type: text/plain; charset=ISO-8859-1
> > 
> > Hi Greg and List,
> > 
> > Great question Greg.  I'm curious to hear what the experts have to say.
> > 
> > Some OC's start out as white or light-grey - like some LL6 types.
> > That is why some LL6 meteorites are mistaken for lunars or eucrites -
> > because they lack chondrules and have that whitish color.
> > 
> > Best regards,
> > 
> > MikeG
> > 
> > ----------------------------------------------------------------------
> > Mike Gilmer - Galactic Stone & Ironworks Meteorites
> > 
> > Website - http://www.galactic-stone.com
> > Facebook - http://www.facebook.com/galacticstone
> > News Feed - http://www.galactic-stone.com/rss/126516
> > Twitter - http://twitter.com/galacticstone
> > EOM - http://www.encyclopedia-of-meteorites.com/collection.aspx?id=1564
> > -----------------------------------------------------------------------
> > 
> > 
> > 
> > On 3/30/11, Thunder Stone <stanleygregr at hotmail.com> wrote:
> >> 
> >> Hi List:
> >> I hope everyone is well.
> >> I have a question regarding the 'color' of OC's through staining by some
> >> mineral influx or by oxidation.  It appears most fresh OC's start out as a
> >> light beige or tan color; then through time the metal rusts and they often
> >> turn yellowish, orange, or brownish - this make sense.  My questions is
> >> this:
> >> What other colors can they become, blue or green?  What element(s) result in
> >> different colors?  What different weathering processes are involved?
> >> The reason I ask is because I have a weathered meteorite that is dark green
> >> in color; it looks like jade and I have not seen any like this one before.
> >> I have also and seen OC's with a 'black' color, what causes that?
> >> Thanks,
> >> Greg S. 		 	   		
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> > 
> > 
> > --
> > 
> 
> -----------------------------------------------------------
> Dr. Laurence A.J. Garvie
> Collections Manager
> Center for Meteorite Studies
> School of Earth and Space Exploration
> Arizona State University
> Tempe
> AZ 85287-1404
> USA
> 
> phone: 480 965 3361
> fax: 480 965 8102
> email: lgarvie at asu.edu
> 
> Weblinks:
> School of Earth and Space Exploration:  http://sese.asu.edu/
> Center for Meteorite Studies: http://meteorites.asu.edu/
> 
> -----------------------------------------------------------
> 
> 
> 
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