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BLM Runs Check on Assay Services

May 2003 by Scott Harn

The Bureau of Land Management (BLM) recently conducted a multi-year study of sixty-five assay laboratories to determine the accuracy of their testing procedures. The laboratories, all located in North America, were provided with ore samples of known concentrations without benefit of identifying the source as BLM. Payment was rendered for the service provided.

Most laboratories involved were sent 4 samples containing known values of gold, silver, platinum, and palladium, and 2 samples that were complex blanks. Prices charged for assay services varied from $60, for fire assays, to $2,250 for a “tin fusion method.” In our review of the report, price did not seem to be reflected as a determining factor for accuracy. In some cases, a lower cost for service provided a more accurate assay.

The results of assays conducted are compiled in a 34-page report, including 16 pages detailing the reasons for and methods used in the study, and 18 pages of results. The volume of the report does not allow for inclusion in this publication, but ICMJ’s Prospecting and Mining Journal has made the entire document available free on our web site:

Study preface (.pdf file) 0.8MB
Study results (.pdf file) 1.0MB

Many of the results published were well within acceptable limits, but some were so far out in “left field” that utilization could be disastrous. Substantial quantities of precious metals were reported in some blanks. Some samples that contained valuable quantities of precious metals were reported as “none detected.” As a result of this report, several assay labs were barred from advertising in our publication.

BLM should be applauded for conducting this badly needed study, and hopefully they will continue this public service. The resulting report should be a valuable tool as a validation for assay services.