Thallium contents of 16 USGS standard rocks

Thallium was determined in 16 USGS standard rocks by atomic absorption spectroscopy in which a heated graphite atomizer was used after extraction as thallium iodide into amyl acetate. Four subsamples from four bottles of each standard sample, except G-1 and W-1, were analyzed in random order, and the average thallium contents in parts per million (as Tl) were AGV-1, 0.41; GSP-1, 1.63; G-2, 1.08; BCR-1, 0.35; SDC-1, 0.80; MAG-1, 0.79; BHVO-1, 0.049; SCO-1, 0.79; SGR-1, 0.34; QLO-1, 0.23; RGM-1, 1.07 ; STM-1, 0.30; DTS-1, <0.005; and PCC-1, <0.005. The analysis of variance showed that all samples may be considered homogeneous at F_0.975 and only GSP-1 may be considered heterogeneous at F_0.95. The Tl contents of G-1 and W-1 are 1.0 and 0.12 ppm, respectively.