What Are Standards?

QAQC (Quality Assurance and Quality Control) is a major business imperative for mining companies. In an industry where just .1g of Au or .2% of Fe can mean the difference between success and failure, having confidence in the assay results your lab of choice provides is incredibly important. One particular QAQC tool is the standard or Certified Reference Material (CRM). Standards are a package of rock/soil that looks for all intensive purposes like all the other bags of dirt the lab receives but with one major difference. The chemistry of that bag of rock/soil is already known to a very high degree. The lab processes this package in the same manner as it processes all the other samples and reports back accordingly. The site geologist who then receives the assay results should first compare the assay results of the inserted standards to their certified chemistries. If the two are comparable, then the batch assay results can be trusted and utilised. If the lab reports chemistry for the inserted standard that varies greatly from the certified chemistry of that standard, then the batch assay results can't be trusted. Major differences between standard certified chemistry and standard lab assayed chemistry can be put down to many things but they are generally all internal lab processes. This may be poor sample prep, machine drift/calibrations issues etc. Most of the time labs will keep pulped samples of the batch and it may be, in the case of a failed standard, that the lab re-assays the whole batch. Once this is done, the standard will again be considered first. Then, once the standard has passed the comparison test, the batch assay results can be trusted and utilised. Standards are generally created by companies external to the mining company from material provided by the mining company. They are generally created from material that the mining company would consider ore. Standards can either be pulverized or coarse samples. The standard, should, for all intensive purposes, appear the same or roughly the same as any normal sample. Standards are created by drying and milling a bulk sample of that supplied ore and then splitting it down into smaller, representative packages. Once a batch of standards has been created, a random selection of samples will be taken to be sent to the umpire labs. Theses randomly selected samples must be indicative of the whole batch in average chemistries. In addition to this, the assay results given by the umpire labs cannot exhibit large scale deviation from the average chemistry. Good consistent chemistry of all umpire samples combined with very small standard deviations of that chemistry will indicated a good standard.