Optical, infrared, EPR, and thermoluminescence emission spectra are measured for color centers in natural and X-ray irradiated sanidine. These and the kinetics of color center formation and destruction indicate the presence of several kinds of closely related centers. Preferential migration of cations along the b-axis of the crystals and dominant optical absorption by hole centers can be inferred from electrolytic coloration experiments. A model for these hole centers consisting of a hole on oxygen in a cluster of three adjacent aluminum ions is proposed. Four types of these clusters are possible in the feldspar structure. Two of them should allow hopping of the hole between two equivalent oxygen ions. Like in the smoky quartz centers this should result in strong optical absorption. The polarization of the optical absorption bands is in good agreement with this model.
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Speit et al. (1976) studied this question.
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