thermoluminescence

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Release, in the form of a light pulse, of stored nuclear energy in a mineral substance when heated to perhaps 500°C/930° F. The energy originates from the radioactive decay of uranium and thorium, and is absorbed by crystalline inclusions within the mineral matrix, such as quartz and feldspar. The release of TL from these crystalline substances is used in archaeology to date pottery, and by geologists in studying terrestrial rocks and meteorites.

Thermoluminescent dating
Crystalline substances found their way into the clay fabric of ancient pottery as additives designed to strengthen the material and allow it to breathe during kiln-firing at 600°C and above. Firing erased the huge level of TL energy accrued in geological times and sets a ‘time-zero’ for fresh energy accumulation over archaeological times, the TL intensity measured today being proportional to the pottery's age. TL can date inorganic materials, including stone tools left as burnt flint, older than about 50,000–80,000 years, although it is regarded as less precise in its accuracy than radiocarbon dating.

Green, red, and blue were the colours of the Eritrean People's Liberation Front (EPLF) flag which bore a yellow star at the hoist. Effective date: late 1995. >>