The following terms are used here and in literature elsewhere to discuss reference materials.
There are currently 10 names in this directory beginning with the letter S.
Standard reference material, synonymous with reference material or certified reference material. Note: in the past this acronym has also been used for “Secondary Reference Materials” – materials characterised to a lower level than and generally not conforming to all ISO criteria for a CRM.
The South African Code for the Reporting of Exploration Results, Mineral Resources and Mineral Reserves (the SAMREC Code).
The South African Council for Natural Scientific Professions (SACNASP) was set up by the Natural Scientific Professions Act of 2003 but is now adminstered by a new version of the Act passed in 2013. SACNASP registers all Natural Science practitioners within South Africa and in the mining industry. It is relevant to all geologists and chemists writing technical reports about mineral exploration or mining or otherwise or providing a service to the South African public. This will include all geologists acting as consultants and/or writing reports for publication by JSE listed companies and all chemists signing off assay results customers or public companies. According to the Act it is illegal within South Africa to practice and provide a service to the public as a geologist or a chemist unless registered with SACNASP. The 2003 Act punished miscreants with a fine or prison. This was watered down in the 2013 Act to just a heavy fine. Registration in essence is a process whereby the qualifications of an applicant are confirmed to be true, valid and relevant to the field of practice specified. Registered geologists and chemists will list Pr.Sci. Nat. on the report after their name.
Literally this refers to a recognised and approved method or procedure (such as the standards published by ISO) but its use to describe reference materials is also well entrenched in the mineral and chemical industries.
To be fit-for-purpose, RMs should be sufficiently stable so that the end user can rely on the assigned value at any point within the period of validity of the certificate. Stability should be considered under long-term storage conditions, under transport conditions and under the storage conditions of the end user. This can include consideration of stability after opening, if re-use is permitted.
The required mass of material to achieve a 1% RSD using the known relationship between sample mass and SD (see Ingamells, C. O. and Switzer, P. (1973), Talanta 20, 547-568). This parameter is important as it provides users with a quantitative indication of the CRM’s level of homogeneity. Users require irrefutable data on the magnitude of CRM sampling errors and their impact on QC protocols. An article
published in the EXPLORE newsletter for geochemists shows that some manufacturers are showing micro-nuggets in their gold CRMs.
By virtue of differences in size and physical property (volume, density, shape, etc), particles will differentially move (segregate) from one location to another. This is particularly important for metal concentrations in Certified Reference Materials (CRMs) given that the sample provided is typically sub-sampled for analysis which may or may not be representative and true to its certification. Particle segregation is particularly ubiquitous during powder handling and transfer and is most pronounced in free-flowing powders. Powders that tend to agglomerate are inherently not free flowing and exhibit high levels of cohesion and adhesion. This ‘sticky’ manifestation can only be overcome by mixing devices that employ high shearing forces or subject the powder to impact. However, when these types of powders have been mixed (homogenised) they are far less susceptible to segregation due to the high inter-particulate forces that resist inter-particulate motion that leads to unmixing.
Standard Combined Uncertainty
It is the estimated standard deviation, equal to the positive square root of the total variance obtained by combining all uncertainty components. Standard Uncertainty is the uncertainty at 1 Standard Deviation level or at roughly 68.3% of probability in the normal distribution curve.
Standard Deviation (SD, sd or s)
A measure of the spread or dispersion of a set of results and calculated from the square root of the variance.
A single result or entire set of results deviating in either accuracy or precision from others in the set or from other sets, respectively, to a degree greater than can be justified by statistical fluctuations associated with a given frequency distribution.