| In this paper, heat treatment experiments on sapphires from Shandong province, China, have been undertaken.It mainly includes removing taxtic colors or needle inclusions, and lightening deep blue hues. On these bases, study on heat treatment theory has been going on. In the end, it reach the following results: A. With chain transfer of point defect in the sapphire crystal, divalent irons can be changed into trivalent irons in the oxidixing atmosphere; B. The relationship between lasting time at maximum temperature( t )and radius ( r ) of sapphire is:d t t =2d r r ;C. Rate of decreasing temperature is less than φ= RSf(T) r 2; and D. Besides intensification of transfer transition between di_ and trivalence irons, increasing of population of liquid or gas inclusions in nanometer scale are account for gray hues in treated sapphires. |