The rock the CRM’s are made from is milled down to a very fine powder, homogenized and packaged. Then the batch is scientifically sampled. These samples are sent to laboratories all over the world for interlaboratory testing. The results are complied, the consensus mean calculated and limits set within which a laboratory using these control samples should be able to report 95% of their results. The manufacturing, sampling, statistical treatment of the data and certification are more fully described in the Certificates for these products published on the AMIS website www.amis.co.za.