Obsidian hydration dating limitations

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The mounted specimen slide is ground in a slurry of 600 grade optical-quality corundum abrasive on a plate glass lap.

This initial grinding of the specimen reduces its thickness by approximately one half and removes any nicks from the edge of the specimen produced during cutting.

The hydration–rind dating technique also has been used to date glassy rhyolitic flows that have erupted more than 200 years ago but less than 200,000 years ago.

The reconstruction of time is a central concern all archaeologists must address in their research; few, however, are fully aware of the potential of all the dating methods at their disposal.

Narrow rinds (under approximately two microns) are usually examined under a higher magnification.

The prepared slide is measured using an Olympus BHT petrographic microscope fitted with a video micrometer unit and a digital imaging video camera.

When a clearly defined hydration layer is identified, the section is centered in the field of view to minimize parallax effects.

Two parallel cuts are made into the edge of the artifact using a lapidary saw equipped with 4-inch diameter diamond-impregnated .004″ thick blades.

These cuts produce a cross-section of the artifact approximately one millimeter thick which is removed from the artifact and mounted on a petrographic microscope slide with Lakeside thermoplastic cement. A New Dating Method Using Obsidian: Part I, The Development of the Method.

Standard deviation values for each measured surface indicate the variability for hydration thickness measurements recorded for each specimen.

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