The 18 Chinese geochemical standard reference samples GSD 9-12 (stream sediments), GSS 1-8 (soils) and GSR 1-6 (rocks) were prepared after GSD 1-8 (stream sediments) for even wider and increasing needs of geology, exploration geochemistry and geochemical analysis. Usable values of 41 trace, minor and major elements of the 18 samples were published in 1984. In the following two years, efforts were concentrated on the determination of other elements, most of which are more difficult to determine accurately and hence not many data were available in the literature. At the same time, additional data on the 41 elements already evaluated were also submitted. In all, 155 234 results were available along with the 35 284 analytical data submitted. The processing of samples, the examination of sample homogeneity, the plan of collaborative analysis of the samples, and the criteria for defining the recommended values are described. The recommended or reference values of the 72 constituents, to-gether with the 35 284 analytical data of the 18 samples are published in this paper.

Geochemical standard reference samples gsd 9–12, gss 1–8 and gsr 1–6

Recommended concentrations for 38 elements in the U.S. Geological Survey reference sample, Ohio Shale (Devonian) SDO-1, are presented here. For an additional 25 elements, average concentrations or ranges are reported for information. Also presented are the supporting analytical data and a description of the statistical procedure used in deriving recommended concentrations from that data. The sample is a brownish-black, fissile, platy shale containing flattened pyrite nodules and a high organic content. It is typical of “eastern gas shale”, in contrast to the USGS reference sample SGR-1, which typifies oil shale from the Green River Formation. SDO-1 was collected from the Huron Member of the Late Devonian Ohio Shale in western Rowan County, Kentucky. The sample is available as fine splits for detailed chemical analysis and as coarse splits for hand, microscopic, and microfossil examination.

Characterization of Devonian Ohio Shale SDO‐1 as a USGS Geochemical Reference Sample

The use of geologic reference samples may have started in the last quarter of the 19th century after analysts in England, Germany, and the United States deplored the large variation in data obtained by different analysts for the same constitutent in the same sample. Early samples involved in cooperative analysis, also known as “round robins,” were mainly industrial or agricultural materials of economic value, or products derived from them. Data from some round robins were so diverse that “uniformity in analysis” was a part of early committee names. The first two geologic samples of the National Bureau of Standards were analyzed cooperatively.



Samples for geology and geochemistry are classified as artificial samples or as natural materials of either economic or geochemical interest—the latter distinction not always possible. Artificial samples have been prepared in several substrates, and samples in other substrates may be limited only by the ingenuity of the analyst.



The principal suppliers of samples of economic interest are discussed, by country, to show the range of samples prepared by organizations. Natural samples of geochemical interest are mentioned by sample type. Because of their intended use, some geochemical samples are restricted to analysts using specific techniques.



Methods used for and precautions to be observed while preparing large or small rock samples are discussed. Excess grinding of small rock samples reduces the amount of FeO found in a rock analysis. Unavoidable contamination occurs when processing rocks in steel. Tungsten carbide, and some mechanical equipment, should be avoided. A review of the allied subjects of homogeneity of a sample, sampling errors, and size of the sample grains shows that we have reinvented the wheel since 1885.



Methods used tc (1) test the homogeneity of samples, (2) eliminate outliers which some scientists reject repeatedly despite warnings of statisticians, and (3) estimate best values when the method for estimating should be part of the program for a sample are discussed. Calibration lines may be used to determine if “best values” in a series of several samples are really “best” and to furnish confidence limits for a single datum.



The agreement of data by an analyst for a reference sample with data preferred by an issuing organization is usually described by one of several adjectives, a subjective procedure. A variation of a x2 method may be used if a producer specifies the exact number of data for the cooperative analytical program to be furnished by each analyst and then calculates the population estimates of the mean and standard deviation for an element in a sample.



Because of the large increase in the number of reference samples of all types, a revised table listing samples that may be useful in geochemistry is included. It is not known if the samples, other than those of the U.S. Geological Survey, were collected in conformance with provisions of the Plant Pest Control Regulations of the U.S. Department of Agriculture, or of similar organizations in other nations.

Reference Samples in Geology and Geochemistry

Two chromitite samples from the Isles of Shetland (North Scotland) have been processed, each in 200 kg quantities, as reference samples for the determination of gold and the platinum-group elements (PGE). One of these samples, Chromitite CHR-Pt+ is enriched in the PGE and the other, Chromitite CHR-Bkg has much lower concentrations. A detailed assessment of sample homogeneity is presented, together with the results of a cooperative study by thirty-five international geochemical laboratories, private and public. Contributed data together with derived working values are presented for Au and the PGE as well as for major, minor and a few trace elements. It is hoped that this first compilation report will encourage additional laboratories to participate in further studies of the PGE in these two CHR samples.

Preparation, homogeneity evaluation and cooperative study of two new chromitite reference samples chr-pt+ and chr-bkg

Reference samples for use in analytical geochemistry: their availability, preparation, and appropriate use

The presence of outliers and the statistical noise that affects the data for reference materials have undesirable effects on the mean and on other indicators of the central value. Five robust indicators of the central value, which are resistant to obvious outliers and less obvious contamination (spurious data), were investigated: the dominant cluster mode, the modian, the Gastwirth median, the trimean, and the trimmed mean. The mean and the median were investigated for purposes of comparison.



The results confirm that the mean is very unreliable, and that the Gastwirth median and the dominant cluster mode are strong indicators of the central value.

Five Robust Indicators of Central Value

Measures of material variation (state of homogeneity) for reference materials of powdered rocks, minerals, and ores are examined critically.



It is shown that the customary analysis of variance concluding with the F-test is not a satisfactory method for the analysis of the analytical data obtained in a homogeneity experiment. It is argued that an estimation approach is more appropriate.



Examples are given of values calculated from reference-material data, together with an explanation of how the results can be interpreted.

Estimation of Material Variation In Powdered Materials

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Five Robust Indicators of Central Value

Estimation of Material Variation In Powdered Materials