buddie421there are some very good research papers on assessing diamond potential of kimberlite, sampling and statistical modeling on th rex diamond mining web page. could not link because the server keeps booting me out. try www.rexmining.com. one of the papers suggests it is common for a kimberlite pipe to have a grade of .2 carats / ton in the crater facies and 0.8 carats/ton in the diatreme facies. sound familiar?