[meteorite-list] Meteorite?

From: Randy Korotev <korotev_at_meteoritecentral.com>
Date: Wed, 30 Nov 2011 12:12:10 -0600
Message-ID: <201111301808.pAUI88S03747_at_levee.wustl.edu>

I measure the specific gravity of most of the rocks that people send
me. The book values for the SG of hematite and magnetite are in the
5.1-5.3 range. I get a lot of hematite and magnetite rich rocks, and
SG's range from 3 to 5. The low ones are usually from rocks with
quartz sand cemented by a lot of hematite or, perhaps better,
hematite diluted with quartz sand.

I also get a lot of rocks that are claimed to contain metal but all I
can see are shiny mica flakes and grains of pyrite or arsenopyrite
that look like metal but aren't. As I say on this page, a good test
is to look at the grains after sawing and see if you can see the saw marks.

http://meteorites.wustl.edu/id/ordinary_chondrites.htm

If you can't, it's probably not FeNi metal. I'd like to see the sawn
face of the stone in those photos up close.

Ordinary chondrites break apart from weathering in nature because the
metal rusts, causing a volume expansion (like rust blisters under
automobile paint) that fractures the rock making it easier for water
to get in, etc.. That's the only environment I'd expect to see a lot
of hematite together with metal. The rock in the photos doesn't seem
fractured.

Randy Korotev




At 10:00 PM 2011-11-29 Tuesday, you wrote:
>Hi Mike and thanks for your opinion. I seem to see some tiny
>vesicles but can't be sure; also we can't assume it's metal that's
>sparkling and my thoughts are at a density of 3.2 g/mL it is
>possibly some sort of basalt. Anyway, it's a very interesting
>meteorwrong, (assuming it's a wrong from the streak test which may
>be at odds with it being basalt ...). Wonder what Randy would think
>about it; the rock was found in the midwest not too far from
>him. It'd be a good one for his great site. Probably can strike it
>down as a meteorite by thinking about the two tone concentric heart
>it has with dendrites coming out (second picture). Still puzzled...
>
>Kindest wishes
>Doug
>
>
>-----Original Message-----
>From: Galactic Stone & Ironworks <meteoritemike at gmail.com>
>To: MexicoDoug <mexicodoug at aim.com>
>Cc: Jimski47 <Jimski47 at aol.com>; meteorite-list
><meteorite-list at meteoritecentral.com>
>Sent: Tue, Nov 29, 2011 8:34 pm
>Subject: Re: [meteorite-list] Meteorite?
>
>
>Hi Doug and List,
>
>Except for the grain size, it reminds me of some acapulcoites,
>visually speaking. And if not for the metal flakes, it reminds me of
>a very finely grained angrite.
>
>Best regards,
>
>MikeG
>
>
>--
>Galactic Stone & Ironworks - Meteorites & Amber (Michael Gilmer)
>
>Website - http://www.galactic-stone.com
>Facebook - http://tinyurl.com/42h79my
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>Twitter - http://twitter.com/galacticstone
>
>
>
>On 11/29/11, MexicoDoug <mexicodoug at aim.com> wrote:
>>Looks like this has been commented on a bit and confirmed as a -
>>meteorwrong - and apparently streaked reddish since it is commented
>>that a streak test indicated it was probably hematite. (The color
>>isn't mentioned, only that the streak proved it was hematite was
>>mentioned.)
>>
>>just one comment, it would be nice to have these threads in the forum
>>since having to sign up on another site if the thread is started there
>>twists up the thread ...
>>
>>here are the interior pictures:
>>
>>http://www.meteoritejunction.com/download/file.php?id=1121
>>
>>http://www.meteoritejunction.com/download/file.php?id=1122
>>
>>Also, this stone is stranger in my opinion than that.
>>
>>The OP mentions it has a density of around 3.1 g/cc and says that
>>hematite has a density of about 2.7 g/cc, and accounts for the higher
>>density being caused by metal flakes distributed throughout the
>matrix.
>> Hematite is muich heavier than 2.7 g/cc, after all in broad terms,
>40%
>>of its chemical formula is iron so one, ignoring the packing, could
>>guestimate the minimum density of hematite at 0.4*(8 g/cc) = 3.2 g/cc,
>>but given that the oxide has some weight, hematite ought to have a
>>density of between 4-6 g/cc (and they are around 5.2 g/cc for both
>>magnetite and hematite, depending on how it 'settles' together).
>>Probably the 2.7 g/cc referred to was for quartz terrestrial rocks,
>not
>>oxides of iron.
>>
>>In any case, I wonder if anyone else has experience with metal flakes
>>in hematite. Hematite one of the most highly oxidized forms of iron
>>right up there, more than goethite, and what can result when magnetite
>>oxidizes further. I makes me wonder how you could have metal flakes
>>survive in a hematite matrix (I don't think this can happen but really
>>would like to know if anyone has seen this, for all I know there is a
>>common process that can produce this, though I can't imagine what it
>>would be unless someone mixed up a batch specially to do it).
>>
>>ref:
>>http://www.meteoritejunction.com/viewtopic.php?f=10&p=2860#p2860
>>
>>Kindest wishes
>>Doug
>>
>>
>>
>>
>>-----Original Message-----
>>From: Jimski47 <Jimski47 at aol.com>
>>To: meteorite-list <meteorite-list at meteoritecentral.com>
>>Sent: Mon, Nov 28, 2011 3:54 pm
>>Subject: [meteorite-list] Meteorite?
>>
>>
>>Hope everyone had a nice holiday weekend. I did some meteorite hunting
>>and
>>found this stone. I'd like to get some feedback on it.
>>_http://www.meteoritejunction.com/viewtopic.php?f=10&p=2860#p2860_
>>(http://www.meteoritejunction.com/viewtopic.php?f=10&p=2860#p2860)
>>
>>
>>Cheers,
>>Jim K
>>
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Received on Wed 30 Nov 2011 01:12:10 PM PST