"A problem with RCD is the potential for contamination. If gold...

"A problem with RCD is the potential for contamination. If gold is encountered in a drill hole in any significant concentration, this gold can be smeared by the bit for a distance down the hole, and can be smeared up the hole if the compressor is not large enough to push the cuttings completely up the pipe. The resulting assays can appear to be from a wider interval than is actually the case. RCD cuttings are usually analyzed by geochemical methods to start with, then followed by assay methods if significant mineralization is found. The RCD method is relatively inexpensive, with drilling costs usually less than $10 per foot."

http://grcir.com/c34d92a2-36cf-4ea8-aee0-469a8a586e22.aspx?r=95ee97f1-705b-4c34-aa0b-3cc335d48e04

But surely everyone was aware it was RC , not diamond ?