[meteorite-list] triolite inclusions

[John Keefner]

Hi all,

A quick question regarding rounded troilite inclusions in iron meteorites...

I believe FeS has a significantly lower melting temperature (around 1000 
degrees C) than the Fe-Ni alloy (around 1450 degrees C) that make most iron 
meteorites. In a cooling planetismal, wouldn't one expect that troilite 
would be the last dregs of molten liquid remaining in the cracks between 
crystallized Fe-Ni? If that were the case, wouldn't troilite be expected to 
be a 'filler', with an elongated morphology? So, why does troilite occur in 
rounded inclusions?

Perhaps rounding from grain boundary diffusion occurs on a long time-scale 
or the blebs are an indication of late stage impact melting and rapid 
cooling... I'm not sure that I buy the surface tension idea where troilite 
separates out from an ocean of liquid Fe-Ni alloy.

Thanks,
John

From: MexicoDoug at aol.com
To: steve_arnol60120 at yahoo.com, meteorite-list at meteoritecentral.com
Subject: Re: [meteorite-list] triolite inclusions
Date: Mon, 3 Jan 2005 11:51:26 EST

Hola Steve,

I think Tri-o-lite is a dead brand of the dead Urelite Corporation.

On the other hand, Troilite, named for the Italian Jesuita Abbé Domenico
Troili of Villa Albareto meteorite fame.   The 1766 Italian  witnessed fall,
Troili collected eyewitness accounts of what he actually  believed was a 
volcanic
discharge into the atmosphere.     Troilite was named after him since he
collected some of the stones - yes it was  first observed in "modern" times 
from
the University of Modena, Ferrari town,  Italy, in this L5 stone meteorite.
EvNot an iron meteorite.   Troilite's account led it to be understood as 
pyrite
(fool's gold), but a few  decades later Howard of Howardite fame set the 
woirld
straight on thatshowing it  was an iron sulfide but different from the
earthly ones because it was  NON-magnetic, unlike the earthly counterparts.  
Anyway
in 1863 Troili got  the honor and it was named "Troilit" by Rose in Berlin
after he  demonstrated that it was balanced FeS and recognized Troili's 
attempt
at  description of it nearly one hundred years earlier.   In English,  
Troilit
would be Troilite...

So...Troilite is just a charged balanced Fe-S hexoganol pyrrhotite, in  
other
words, ferrous sulfide.  Why it gets into the iron meteorites to me  is a
question with philosophical overtones like why is the sky blue.  The  stuff 
is
found in many mines as pyrrhotite, the similar earthly mineral which  almost
always has an excess of sulfur with it.  In other words, FeS iron  
defficient
where both have a plus two valence shell.  But if you look at it  another 
way,
considering the interior of planetesimals iron meteorite foundries,  you 
might
say the creator accidentally contaminated the iron with sulphur.   That is 
why
if you grind the mineral your pet blobs can stink on ice like  rotten eggs.

Sulfur isn't the only contaminant in the meteoritical material.  There  is a
host of stuff like Iriduim in traces, too.  Or oxygen in carbonaceous
meteorites.  So where you get a nice oxide with oxygen, you might get a  
nice sulfide
with sulfur.  Putting the sulfur in the foundry and then  getting the
blobules you like might be caused by physical events internal in the  
meteoritical
foundary.  Perhaps when all is molten to start with, the iron  nickel form a
nice alloy not too miscible with the troilite, so they naturally  separate, 
just
like you shaking up a bottle with oil and water and watching the  blobs form
of the separate phases (aquaeous and organic).  Or perhaps the  high
pressuressquish it into imperfections in the iron nickel alloy as it cools,  
like
squashing a Miller can in your hands, maybe it sort of aggregates  through 
the
conduits that are available.  But that really isn't likely in  my opinion as 
the
first, because they are usually rounded or spheroidal  indicating more of a
miscibility (mix-separation) issue.  A sphere like  shape is formed because 
it
minimizes the surface exposed for a given volume when  stuck in an 
unfriendly
environment.  That's why babies are in the fetal  position and girlfriends 
too,
when they are left cold and alone.:)  And  raindrops look that way and maybe
tektites sort of, too...

Troilite by no means is limited to occur in iron meteorites, so the creator
has contaminated stoney meteorites with it too, as was first observed
meticulously by Troili.and there is some in the samples of lunar soil 
brought  back
from the Apollo missions as well.

Hope this helps your thirst for knowledgof the rockin our  showcases....
Saludos and thanks for the Christmas present "freebee",  Doug
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