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Eighteen pyrite and twelve marcasite samples which have different provenances have been investigated to determine the systematics of the influence of mineralogical and geological factors on the "Fe Miissbauer spectra at 298 K. The following results have been obtained: there is no ambiguity in distinguishing single phase pyrite from single phase marcasite by means of "Fe Miissbauer spectroscopy at 298 K. At 298 K the average electric quadrupole splitting, (AEo), and average isomer shift, (6), with respect to Fe metal, are 0.61 IO It 0.0030 mm SC' and 0.313 f 0.008 mm s-', respectively, for the I8 pyrites; (A&) = 0.5030 ? 0.0070 mm s-' and (a) = 0.2770 + 0.0020 mm s-r for the I2 marcasites. At 77 K, AE, is 0.624 mm s-' for pyrite and 0.508 mm s-' for marcasite. In distinguishing pyrites from marcasites, spectra obtained at 77 K are not warranted. The Mdssbauer parameters of pyrite and marcasite exhibit appreciable variations, which bear no simple relationship to the geological environment in which they occur but appear to be selectively influenced by impurities, especially arsenic, in the pyrite lattice. Quantitative and qualitative determinations of pyrite/marcasite mechanical mixtures are straightforward at 298 K and 77 K but do require least-squares computer fittings and are limited to accuracies ranging from lt5 to 215 per cent by uncertainties in the parameter values of the pure phases. The methodology and results of this investigation are directlv aDDlicable to coals for which the Dresence and relative amounts of pyrite and marcasite could he of considerable genetic significance.

Three methods for the energy‐dispersive x‐ray spectrometric analysis of trace elements in silicate rock samples were compared. The comparisons were based on three new USGS reference samples, DNC‐1, W‐2, and BIR‐1, and two established reference samples, G‐1 and W‐1. A loose powder sample preparation was used in the analysis of selected trace elements, including Ni, Cu, Zn, Rb, Sr, Y, Zr, Nb and Ba. For one method, the ratio of analyte line intensity to either Compton or Compton and Rayleigh scatter intensity for a series of standards was used to construct calibration graphs. The other two methods involved fundamental parameter calculations which required a knowledge of the total sample compositions in order to perform the necessary matrix corrections. The results showed good accuracy for all three methods, but those obtained from the ratio–calibration graph method were slightly better than those from the other two methods.

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