NWA 4478 Lodranite: mystery rainbow feature

NWA4478-lodranite-rainbow

Mystery solved: UPDATE (7/28/2012):  After receiving my new microscope, I was able to view the area at much higher magnification.  I very carefully used an X-Acto knife to gently scrape the area and the film causing the rainbow does come off.  There appears to be a thin film of something on the specimen (reminds me [...]