

 20 



15 - 



10 — 



NATURAL 



100 200 300 400 



TEMPERATURE -CENTIGRADE 



Figure 10-7. Increase in thermoluminescence produced by ex- 

 posure to gamma radiation. Glow curves for Escabrosa 

 limestone. 



cite in solution at a rate which can be controlled under laboratory conditions 

 ( Wray and Daniels, 1957) . The change-over from aragonite to calcite is a factor 

 in the thermoluminescence glow curve. 



The structure of limestones varies greatly. If the rock contains small fossils, 

 these will have different impurity concentrations than the imbedding crystal 

 structures and give rise to different thermoluminescence intensities. 



Dolomites give a different thermoluminescence glow curve than do mixtures 

 of CaC0 3 and MgCOs- This difference may be due to differences in the crystal 

 lattice, or it may be due to differences in the impurities that are taken into the 

 dolomite and calcite crystals. 



191 



