[meteorite-list] Odd Rock - Is it...?? Pyrite Plus

From: E.J <jonee_at_meteoritecentral.com>
Date: Thu Apr 22 10:17:39 2004
Message-ID: <3FD0671D.8010403_at_epix.net>

MexicoDoug_at_aol.com wrote:

>
> http://www.geocities.com/sstelenes/rocks.html
>
> The above link is a page with three photos and a description of an odd
> "stone" from Mexico.

Welcome to the list Doug.

Thanks for posting the photos and providing size data.

The "gunmetal gray" would ordinarily suggest Galena an ore of lead which
weathers to a white ashy luster. However, the crystal habit doesn't
match. It is not Galena (Pb lead) or, Fluorite(Ca F), nor is it a
silicate(Si O).

My impression is that it is an Iron Sulfide in the Pyrite class(Fe S)--
there are several variants. We normally think of Pyrite as coming in
cubes but when it is extensively twinned and intergrown like this
specimen, it can look like it has triangular crystal faces. When you
truncate( chop off) the corner of a cube it forms a triangle.

Otherwise-- but unlikely, this could be a "psuedomorph". That is--
another mineral replaces an original crystallized mineral after the
pattern of the original form. In fact on some of the faces I see a hint
of Hematite which is an Iron Oxide. The reverse appears to be
mineralized with Hematite and Limonite(yellow colored) which is is a
"hydrated " Iron oxide. Limonite is an amorphous catch-all mineral name
for the residue left from decomposition of other Iron minerals.

All considered, I believe this is a slightly weathered iron pyrite
crystal cluster, aka Fools Gold. It doesn't have the normal brassy
pyrite color because of the Hematite coating. Not uninteresting but,
not a meteorite as you already know.

Tis another case of anything strange" must be a meteorite" and is a
common meteorwrong theme.

Regards,
Elton
Received on Fri 05 Dec 2003 06:08:13 AM PST