[meteorite-list] Rainbow effect in an specimen of NWA 4478 Lodranite

[Mendy Ouzillou]

Dear list members,

I received, just today, two Lodranite specimens: an 11.42g end-cut of NWA
4478 and a 9.71g end-cut of NWA 6075.  Both specimens are beautiful and the
NWA 6075 exhibits an interesting shimmer effect.  However, when I looked at
the face of the NWA 4478, I was shocked to see what can only be described as
a rainbow about 2mm x 3mm (see image in link, will try to get better one up
in the next few days).

http://www.meteoritesusa.com/blog/nwa-4478-lodranite-mystery-rainbow-feature
/
Now the first thing that came to mind is that some oil was trapped in the
structure and created the thin-film physical effect (think oil slick).  On
further inspection, there were no other areas that displayed the same effect
though there are similar areas where oil could get trapped.  I remembered
seeing something similar on the www.meteorites.com.au website in an Al
Mahbas specimen, but this looks distinctly different.
Oil contaminant or a genuine unusual feature in this lodranite - help me
solve the mystery.

Thank you and any information provided to help me solve the mystery will be
used in any updates to the blog post.

Mendy