Hello PIGs, Essay #13, the last of them, is now posted on the PIG page. The essay pertains to the classification of pegmatites based largely on the scheme proposed by Petr Cerny. Two articles that debated the lithologic versus tectonic controls on the elemental signatures of pegmatites are posted along with the essay by permission of the Mineralogical Association of Canada. David London Pegmatite Interest Group: http://www.minsocam.org/msa/Special/Pig/