MCI Project Summaries 2008 - Smithsonian Institution

MCI 6198 Mineral Microprobe Standards
MCI Staff: Judy Watson
Twenty-six mineral and glass standards from the Mineral Sciences department of the
National Museum of Natural History were analyzed using SEM-EDS in order to determine the
precision and accuracy of our instrument both under ideal analytical conditions and under the
less than ideal conditions that are commonly used at MCI in order to offer non-destructive
analysis to our clients.
MCI 6199 Volcanic Glass Particles in Archaeological Sediment
MCI Staff: Judy Watson, Nicole C. Little, Mel J. Wachowiak
Microtephrochronology is a stratigraphic dating method used by archaeologists and
Quaternary scientists involving the location and characterization of volcanic glass particles
present in soils and sediments in sizes and amounts invisible to the unaided eye. Accurate
determination of the presence or absence of volcanic shards in a soil or sediment sample
precedes quantitative analysis. This determination is typically accomplished using optical
microscopy and is one of the most time-consuming and laborious steps in the process, with great
potential for misclassification or miscounting error. Here a novel method of identifying and
counting volcanic glass particles while simultaneously providing a rough geochemical
characterization of all the particles present in the sample (glass and non-glass), using an Aspex
PSEM 3025 Particle Analyzer with Automated Feature Analysis TM (AFA) software is presented.
An example of a sieved tuffaceous sand showing glass and non-glass grains of various morphologies from the flanks
of Göllü Dağ, Turkey. (Photo: M.J. Wachowiak)
145