What are the procedures for preparation, irradiation, and analysis of lithic samples (i.e., obsidian and chert/flint) at MURR?
Lithic artifacts are cleaned with acetone and deionized water to remove all external markings (e.g., labels, fingernail polish). Obsidian artifact samples for NAA are prepared by either breaking or sawing a portion from the original artifact. The amount removed from the artifact is typically 100–300 mg depending upon the analytical procedure used. An abbreviated-NAA procedure (“short count”) requires only about 100 mg of the sample and works very successfully in most of Mesoamerica (See Glascock et al. 1994) by measuring five or six short-lived elements. If the source cannot be determined by the abbreviated-NAA procedure, the sample should be submitted to our long irradiation procedure, which determines about 20 long-lived elements. The full analytical procedure for obsidian (both shorts and long irradiations) uses 100 mg of sample in high-density polyvials and 250–300 mg of sample in the larger size high-purity quartz tube (6 mm ID by 8 mm OD). In addition, a set of NIST reference mat
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