Umm... I'm no geologist, but?  I'm sure someone could work these two links into the article.

http://encarta.msn.com/dictionary_1861724644/pelite.html
http://www.thefreedictionary.com/pelite
But I doubt you could work this one http://www.jmsplastics.com/thermoplastic/pelite.html P

~ Imagine I swore.