Some physical properties of naturally irradiated fluorite

Abstract

Five samples of purple fluorite found in association with radioactive, materials, and a synthetic colorless control sample were studied and compared. Before and after heating, observations were made on specific gravity, index of refraction, unit-cell size, breadth of X-ray diffraction lines, and fluorescence. The purple samples became colorless on heating above 175° C. During the process, observations were made on color, thermoluminescence, and differential thermal analysis curves. There were strong correlations between the various physical properties, and it was found possible to arrange the samples in order of increasing difference in their physical properties from the control sample. This order apparently represents increasing structural damage by radiation; if so, it correlates with decreasing specific gravity, increasing index of refraction, broadening of X-ray lines, and increasingly strong exothermic reactions on annealing. The differences between the samples in index of refraction and X-ray pattern are largely eliminated on annealing. Annealing begins at 1750 C; thermoluminescence at lower temperatures is due to electrons escaping from the metastable potential traps, not the destruction of those traps which takes place on annealing.