[meteorite-list] Stones with High Troilite, Low Metal

From: Jason Utas <meteoritekid_at_meteoritecentral.com>
Date: Mon, 27 Jun 2011 01:02:19 -0700
Message-ID: <BANLkTimU2wDVXETRzxgJP-obRC4U6+WQVA_at_mail.gmail.com>

Hello Laurence, Doug, All,

>From an NAU site about R-chondrites:

"sulfide rich: pyrrhotite and pentlandite very common, minor troilite;
pentlandite commonly contains Cr up to 2 wt%, troilite may contain Ni
up to 3 wt%"

http://www4.nau.edu/meteorite/Meteorite/Rumuruti.html

Which raised the question -- what is troilite and what is pyrrhotite?

"Pyrrhotite is an unusual iron sulfide mineral with a variable iron
content: Fe(1-x)S (x = 0 to 0.2). The FeS endmember is known as
troilite."

http://en.wikipedia.org/wiki/Pyrrhotite

So, troilite is always pyrrhotite, but pyrrhotite isn't always troilite.

I don't know whether the sulfides in R-chondrites is primarily FeS
where S=1 or S<1, but the distinction is rarely made except in
academic circles. In fact, none of the following top hits goes into
any depth regarding pyrrhotite vs troilite concentrations in
R-chondrites. These were the first three I found:

http://adsabs.harvard.edu/full/1994Metic..29..275S

http://adsabs.harvard.edu/full/1994Metic..29..255R

http://www.sciencedirect.com/science/article/pii/S0009281911000237

- The only source I found in my short quest for knowledge that
bothered to note how much "troilite" is (typically) present in
R-chondrites is the NAU website.

You may well be right, but since troilite is typically present in
rather minor concentrations in most meteorites, I have the feeling
that they are not depleted in it relative to most other types...but I
could be wrong.

For the purposes of Pete's visual observations, I think we can assume
that he meant sulfides in general, since I doubt he has the analytical
capability to tell between FeS (S=1) or FeS (S = 1 to 0.8).

When I saw Pete's note, I immediately thought of R-chondrites,
too...though I wonder if his stone might not be an LL-chondrite. We
have a few R's, and when poked with a neodymium magnet, the pull is
*barely* discernible, to the point that I might call them entirely
non-magnetic if I weren't being careful.

Regards,
Jason



On Sun, Jun 26, 2011 at 6:15 PM, MexicoDoug <mexicodoug at aim.com> wrote:
>
> Hi Laurence
>
> Sulfur stinky yes, I don't think R chondrites are considered troilite rich -
> are they not comparatively troilite poor? That's why I asked why he wasn't
> after pentlandite (and pyrrhotite) as well. The question is pretty useless
> trivia without more information about what the asker is after ... , Sulfur
> (check), Sulfides (check), Low free metals, terrestrial weathering,
> different alterations, they are all bundled up together. I mean, R
> chondrites are loaded with metal but it was oxidized after the formation,
> right? Considering, they are quite troilite poor unless the objective is
> sulfur-rich meteorites and not after troilite after all... maybe perhaps who
> knows
>
> Best Doug
> (Thinking of Mrs. Pennyfeather now!)
>
>
> -----Original Message-----
> From: Laurence Garvie <lgarvie at asu.edu>
> To: meteorite-list at meteoritecentral.com
> <meteorite-list at meteoritecentral.com>
> Sent: Sun, Jun 26, 2011 8:15 pm
> Subject: [meteorite-list] Stones with High Troilite, Low Metal
>
>
> The Rumuruti (R Class) chondrites lack free metal and are sulfide rich.
>
>
> Laurence
> CMS
> ASU
>
>
> On Jun 26, 2011, at 2:19 PM, meteorite-list-request at meteoritecentral.com
> wrote:
>
>> Message: 13
>> Date: Sun, 26 Jun 2011 14:55:17 -0400
>> From: Pete Pete <rsvp321 at hotmail.com>
>> Subject: [meteorite-list] Stones with High Troilite, Low Metal
>> To: meteoritelist meteoritelist <meteorite-list at meteoritecentral.com>
>> Message-ID: <BAY153-w48A18A066F0629249C54C5F8540 at phx.gbl>
>> Content-Type: text/plain; charset="iso-8859-1"
>>
>>
>>
>>
>> Sorry about that - once more with a subject:
>>
>>
>>
>> Hi, All,
>>
>> Is there any particular stone meteorite that has a high content of
>
> troilite
> and a low content of free metal?
>>
>>
>>
>> Cheers,
>>
>> Pete
>
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Received on Mon 27 Jun 2011 04:02:19 AM PDT