Organic Petrology Laboratory
Petrographic Sample Management
Samples received for petrographic analyses in the U.S. Geological Survey Organic Petrology Laboratory are recorded into a log book and into a spreadsheet database. Following sample preparation and analysis, results are returned to the sample submitter via electronic transmittal. Petrographic samples are archived in cabinets and drawers in the Laboratory. Analytical data and associated electronic files (digital photographs, etc.) are retained on computer hard drives in the Laboratory and backed up onto a network server.
Sample Preparation Methodology
Samples submitted to the U.S. Geological Survey Organic Petrology Laboratory usually are prepared for analysis according to the American Society for Testing and Materials (ASTM) Standard Practice D 2797: Preparing Coal Samples for Microscopical Analysis by Reflected Light (ASTM, 2008), or the International Standards Organization (ISO) standard 7404-2: Methods for the petrographic analysis of coal-Part 2: Method of preparing coal samples (ISO, 1985).
Samples are ground to pass a 850-μm (No. 20 mesh) or 1000-μm (No. 16 mesh) sieve in most cases (as-sampled drill cuttings sometimes are mounted for reflectance analysis without grinding). The particulate sample is mounted in a 1-inch mold in a heat-setting thermoplastic powder or epoxy resin medium. Two mounts usually are made for each sample. Examination surfaces are ground and polished prior to overnight drying in a desiccator.
Laboratory Preparation Equipment
Facilities at the Organic Petrology Laboratory include a sample preparation laboratory equipped with sample dividers, sieves, a Buehler Simplimet 3000 automatic mounting press, and a Buehler Ecomet 4 variable speed grinder-polisher. The sample preparation laboratory also contains a fume hood for preparation of larger sample blocks via epoxy resin mounts.
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| Buehler Simplimet 3000 automatic mounting press for sample preparation via heat-setting transoptic powder. |
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Buehler Ecomet 4 variable speed grinder-polisher for preparation of polished sample briquettes. |
References:
ASTM, 2008, Annual book of ASTM standards: Petroleum products, lubricants, and fossil fuels; Gaseous fuels; coal and coke, sec. 5, v. 5.06: ASTM International, West Conshohocken, PA, 720 p.
ISO, 1985, Methods for the petrographic analysis of bituminous coal and anthracite-Part 2: Method of preparing coal samples: International Organization for Standardization Standard 7404-2, 8 p.
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U.S. Geological Survey
