[meteorite-list] Schreibersite & Cohenite

From: Gerald Flaherty <grf2_at_meteoritecentral.com>
Date: Mon Mar 21 13:24:56 2005
Message-ID: <007501c52830$8654e8e0$6401a8c0_at_Dell>

Thank you too Martin. Jerry
----- Original Message -----
From: "Martin Altmann" <Altmann_at_Meteorite-Martin.de>
To: <bernd.pauli_at_paulinet.de>; <meteorite-list@meteoritecentral.com>
Sent: Saturday, March 12, 2005 12:16 PM
Subject: Re: [meteorite-list] Schreibersite & Cohenite


> Hi Jeff and Bernd,
>
> I think, this may be meant for fresh cut samples, as schreibersite and
> cohenite both can show all shades or nuances of yellow or gray, if they
> start to oxydize.
> That's why Norton also suggests a semidestructive test in his book.
> In my practical view schreibersite is more brittle than cohenite, breaks
> off
> more easy while cutting and will be more easilier damaged, if you grind
> your
> specimen by machine and not by hand.
> And my thumb-rule for handpieces is: cohenite doesn't appear in remarkable
> amounts in other irons than those of the IAB-IIICD complex
> (which can of course have additional schreibersite too).
> Furthermore, these wormshaped inclusions, which are oriented parallely to
> the Widmannoops to the fields of the Thomson structures, turned out until
> now always to be cohenite.
> Another observation I made is, that if you find a troilite eye with
> several
> rims of graphite, schreibersite, cohenite, there the cohenite will be
> always
> the more outer rim, than the schreibersite.
> And last but not least, it's impossible to judge from photos, just another
> angle of light and that, was seemed to be brilliant cohenite and that what
> was more dull schreibersite, will be turned otherwise round. You may watch
> out on ebay for a cheap Odessa or Morasko, sometimes also Canyon, which
> has
> both minerals (sometimes in direct contact), so that you have a specimen
> for
> comparing, if you aren't sure.
>
> Buckleboo!
> Martin
>
>
> ----- Original Message -----
> From: <bernd.pauli_at_paulinet.de>
> To: <info_at_meteorites.com.au>; <meteorite-list@meteoritecentral.com>
> Sent: Saturday, March 12, 2005 2:55 PM
> Subject: Re: [meteorite-list] Schreibersite & Cohenite
>
>
>> > Is there a relatively easy and reliable way to visually
>> > pick the difference between Schreibersite and Cohenite
>> > in iron meteorites?
>>
>> Hello Jeff and List,
>>
>> Here is some information from Buchwald that may prove helpful
>> in identifying schreibersite and cohenite in hand samples:
>>
>> Buchwald V.F. (1975) Handbook of Iron Meteorites, Vol. 1:
>>
>> Cohenite (p. 100):
>>
>> - cohenite is brilliant w h i t e
>> - it is very hard, significantly harder than schreibersite
>> - characteristic of group I irons (also occurs in other irons)
>>
>> Schreibersite (p. 104):
>>
>> - schreibersite is magnetic
>> - it is y e l l o w in reflected light
>> - compared to cohenite distinctly more brownish
>> - softer and much more brittle than cohenite
>>
>> See also: O.R. Norton (2002) Cambridge Encyclopedia of
>> Meteorites, Appendix C, Minerals in meteorites (pp. 311-313).
>>
>> Best wishes,
>>
>> Bernd
>>
>> To: info_at_meteorites.com.au
>> meteorite-list_at_meteoritecentral.com
>>
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Received on Sun 13 Mar 2005 07:55:31 PM PST