Mineralogical proficiency testing aligned with the GeoPT programme? Opportunities and challenges - an interactive poster

The GeoPT programme (IAG, 2020) is a valuable tool that allows geochemical laboratories to test their routine analytical performance and, if necessary, undertake remedial action where errors of inappropriate magnitude are detected. During the past 25 years and 63 rounds so far, the GeoPT programme has provided a great variety of rock samples for the benefit of participants. While the GeoPT programme solely focuses on geochemical composition data, it is well known that the mineralogical content of geochemical materials is also of importance to analysts, to researchers and to industrialists (e.g. Meisel et al. 2022). It has long been known that the so-called mineralogical effect can influence the quantitative outcomes of XRF measurements made on pressed pellets. In addition, wet chemical techniques may also suffer from incomplete digestion when resistant minerals are present, unless a rigorous multi acid attack or a combination of fusion and dissolution are employed. The mineralogical content of geological materials is, therefore, important but is not implicitly assessed in the GeoPT programme. Is there a need, therefore, for a dedicated mineralogical proficiency testing programme (MinPT?)?

To our knowledge, there is only one regular mineralogical round robin interlaboratory test programme – the biennial Reynolds Cup (Raven & Self, 2017), which focuses on clay minerals and follows a slightly different approach as the composition of the material is known to the organizers at the outset.

The reason for this interactive poster is to investigate the need for a mineralogical interlaboratory round robin test linked to the GeoPT proficiency testing programme. The idea is that essentially the same material would be distributed in a simultaneous GeoPT and mineralogical test round. Special preparation procedures will be required to ensure that the test material is suitable for both geochemical and mineralogical laboratories operating techniques such as X-ray diffraction, automated mineralogy (MLA, QUEMSCAN, TIMA, etc.) and others. Quantitative mineralogical data from this round robin test would be assessed where possible, using the same well-established GeoPT procedures and providing participating laboratories with personalized performance data. Furthermore, a direct comparison with bulk compositional data from the complementary GeoPT round would permit further insights into analytical performance. It is important to note that there is no expectation that participating laboratories would have to participate in both the GeoPT and mineralogical rounds, but participation in both would be welcomed.

With the help of this interactive poster, we would like to ask delegates for indications of their general interest in participating in a combined mineralogical/geochemical test of proficiency based on effectively the same test materials.

References:

Meisel, T. C., Webb, P. C., & Rachetti, A. (2022). Highlights from 25 Years of the Geo PT Programme: What Can be Learnt for the Advancement of Geoanalysis. Geostandards and Geoanalytical Research.
Raven, M. D., & Self, P. G. (2017). Outcomes of 12 years of the Reynolds Cup quantitative mineral analysis round robin. Clays and Clay Minerals, 65(2), 122-134.
IAG (2020). Protocol for the operation of the GeoPT Proficiency testing scheme. International Association of Geoanalysts (Keyworth, UK), 18pp. http://www.geoanalyst.org/wp-content/uploads/2020/07/GeoPT-revised-protocol-2020.pdf.