z 



UJ TO. 



z 



- 6Q 



CONTROL 



O.I M. Sr 



01 M Sr ♦ Mn. 



50 100 150 200 250 300 350 400 



TEMPERATURE- C* 



Figure 10-8. Effect of impurities on the thernioluminescence of 

 laboratory precipitated calcium carbonate. 



Pitrat (1956) studied the ratio of the intensity of different therniolumines- 

 cence peaks as a function of the magnesium content of limestone. His data are 

 summarized in Figure 10-9. 



Lewis (1956) has studied 18 different similar outcrop samples which show 

 a graduation between calcite and 90 percent dolomite. They were powdered, ex- 

 posed to gamma radiation, and preserved at dry-ice temperatures. Therniolum- 

 inescence glow curves were determined with 50-milligram of powder. Without ir- 



192 



