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An Analysis Of Tachylyte And Other Volcanic Glasses In Washington Archaeology, Mallory M. Triplett

All Master's Theses

Within archaeological literature, a discussion of volcanic toolstones from Washington State is uncommon. Washington’s volcanic glass landscape is relatively sparse, with low-quality sources scattered within and on the east side of the Cascades, including tachylyte, obsidian, and vitrophyric obsidian. Tachylyte is a volcanic glass that forms within low-silica, basalt flows while obsidian comes from high-silica, usually rhyolitic, eruptions. Vitrophyric is a textural term used to describe an igneous rock that has a glassy groundmass with conspicuously large crystals. The low-quality and dispersed nature of these toolstones are reflected in Washington’s archaeological record by the more common occurrence of out-of-state volcanic …