Geochemical and mineralogical data for mine waste from Sulphur Bank Mercury Mine, Lake County, California.

This data release presents geochemical and mineralogical data for mine waste at Sulphur Bank Mercury Mine (SBMM). This work is performed in cooperation with the US Environmental Protection Agency (EPA) to characterize sources of contamination at the SBMM cleanup site. A total of 23 samples were collected: 15 samples were collected by USGS from various waste piles during 2020-21 (14 composites from the top 0-2 centimeters of material, and one composite from six discrete ore hand samples), six composite samples were generated from drill cores from monitoring wells installed by EPA contractor EA Engineering, Science, and Technology, Inc. (EA), in the Waste Rock Dam during 2022. Two additional hand samples - one cinderblock and one scoria - were collected by USGS from the eastern flank of the South waste pile. The 21 composite samples were analyzed by inductively coupled plasma-mass spectrometry (ICP-MS) for trace elements, inductively coupled plasma-optical emission spectroscopy (ICP-OES) for major elements, 5-stage sequential extractions to determine phase associations, semi-quantitative X-ray diffraction (XRD) for mineralogy, EPA Method 3051a for total arsenic and EPA Method 1340 and the California Arsenic Bioaccessibility (CAB) method for relative in vitro arsenic bioaccessibility. The two hand samples were analyzed by ICP-MS for trace elements, ICP-OES for major elements, and semi-quantitative XRD for mineralogy. For composite samples, analyses were performed for two size fractions, S4 (63-250 µm) and S5 (< 63 µm), except for EPA 3051a and 1340 and the CAB test, which were performed on the S3 (< 250 µm) size fraction. The two hand samples were only analyzed for the S5 size fraction. Results are presented for all 23 samples of ore, calcined tailings, waste rock material, Waste Rock Dam drill cores, cinderblock, and scoria collected between November 20, 2020 and June 17, 2022.

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