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Luminescence Dating

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Quartz Glowing Under Black Light

This hunk of quartz fluoresces blue under exposure to black light, because of the presence of impurities.

Sandy Huffaker / Getty Images
Definition:

Luminescence dating is a relatively new method of dating archaeological sites and materials. Although the best known form of luminescence dating is thermoluminescence (or TL), there are several scientific methods which can specify the date of certain artifacts or soil sediments by measuring the amount of light energy they have trapped in the mineral's crystals.

To put it simply, certain minerals (quartz, feldspar, and calcite), store energy from the sun at a known rate. This energy is lodged in the imperfect lattices of the mineral's crystals. Heating these crystals (such as when a pottery vessel is fired or when rocks are heated) empties the stored energy, after which time the mineral begins absorbing energy again.

TL dating is a matter of comparing the energy stored in a crystal to what "ought" to be there, thereby coming up with a date-of-last-heated. In the same way, more or less, OSL (optically stimulated luminescence) dating measures the last time an object was exposed to sunlight. Luminescence dating is good for between a few hundred to several hundred thousand years, making it much more useful than carbon dating.

A Few Recent Studies

Jacobs, Z. and R.G. Roberts 2007 Advances in optically stimulated luminescence dating of individual grains of quartz from archeological deposits. Evolutionary Anthropology 16(6):210-223.

Jacobs, Z., et al. 2006 Extending the chronology of deposits at Blombos Cave, South Africa, back to 140 ka using optical dating of single and multiple grains of quartz. Journal of Human Evolution 51:255-273.

Mercier, N., et al. 2007 Hayonim Cave: a TL-based chronology for this Levantine Mousterian sequence. Journal of Archaeological Science 34:1064-1077.

Porat, N., et al. 2006 Dating the Ramat Saharonim Late Neolithic desert cult site. Journal of Archaeological Science 33:1341-1355.

Examples:
thermoluminescence, optically stimulated luminescence

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