Applications of Reference Materials in the Geological Sciences

The geological sciences are involved in studying the naturally occurring materials of the earth and solar system (i) to understand the fimdamental processes of crustal formation on earth and solar system evolution, and (2) to evaluate the crustal materials of potential economic value to man. Prior to the 1930 s, analyses were carried out exclusively using classical analytical techniques, with detection limits on the order of o.oi-o.i % (mass fraction). The number of elements contained in any sample could be as extensive as the periodic table, but very few of these could be determined. The development of instrumental techniques revolutionized the analysis of geochemical samples, beginning in the 1930 s. 

A significant change in geochemical analysis, and in the demands for natural matrix reference samples to support the analysis of geochemical materials, came with the advent of instrumental methods of analysis. The historical roots of these instrumental methods date from the mid-i88o s to the early 1900 s, but only later were the methods used in routine rock analysis. This use of instrumental methods of analysis generated a demand for rock reference samples, that could be used for calibration purposes. The earliest of them were analyzed by classical methods to determine major and minor oxides 

The development of G-i and W-i (Ahrens 1951 Fairbairn et al.1951 Stevens et al. i960) was the response to this demand with respect to dc arc emission spectrogra-phy. As similar samples are used routinely in calibration for XRF and INAA analyses, many geological samples have been developed as reference materials since that time to support geoanalysis (Potts et al.1992). Just as the change from classical to instmmental methods of analysis changed the nature of demands for reference 

Over 300 geological RMs have been developed over the years. Those listed above have been mentioned in the text, and may be considered representative of the full number available. A complete listing may be found in Potts et al. (1992) or in the July 1994 special issue of Geostandards Newsletter 

---

Applications of geological reference samples to mineral prospecting and economic evaluation of ore potential is the only application with a history dating back before the issuance of G-i and W-i in 1951. It is an area in which data quality or lack thereof has serious economic impacts, hence the very early development of certified reference materials mentioned previously. An extensive study of the state of ore analysis was undertaken by the Institute of Geological Sciences (now the British Geological Survey). Nineteen ores and concentrates, of varied matrix, were distributed to 38 laboratories more than 1532 results were received (Lister and Galagher 1970). 

---