Monday, September 09, 2013

Portable X-ray fluorimeter as an archaeology field tool

I came across this mention of archaeologists using a portable X-ray fluorimeter device to measure trace metal contents in artifacts out in the field. This device can detect small levels of metals, such as Zinc, Rubidium and Strontium, which vary among rocks originating in different volcano systems, thus narrowing down the region in which a rock could have originated.
Watch out where you're pointing that, bucko
For example, obsidian-- volcanic glass-- was highly prized throughout the ancient world because it can be honed into very sharp blades. Obsidian was traded extensively across North America, and an obsidian blade found in present-day Oklahoma might have originated as far away as northern present-day Mexico.  A precise "fingerprint"of the rock helps the archaeologists deduce trading networks, in this case probably involving the Mississippi river and its tributaries.
This X-ray device has a number of advantages, including being non-destructive, fast, and not needing too much sample preparation. However, the device is not yet as sophisticated of the Star Trek "tricorder." It does better with samples of size greater than 1 cm, and is more sensitive toward some metals over others-- thus, even when properly calibrated and operated, it can't always uniquely identify the volcanic source of a specimen.  Still, it's much faster than the Vulcan mind-meld.

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