The optical absorption of gamma irradiated and heat-treated natural quartz

Abstract

Quartz with aluminum as impurity absorbs energy from ionizing radiation and modifies its color. Colorless quartz becomes smoky or dark smoky (morion quartz) when exposed to gamma rays. By heat-treatment, smoky quartz may become successively greenish, yellowish, or brownish as the irradiation dose increases. Natural, colorless quartz is routinely colored by irradiation with gamma rays and heat-treatment for jewelry production. The color formation in natural quartz through this procedure is explained based on EPR, UV-VIS, and IR studies of irradiated and irradiated and heat-treated samples. Smoky quartz shows absorption bands in the visible region and a strong EPR signal. After heat-treatment it shows absorption bands in the near UV region with extensions into the visible region and a weak EPR signal. The intensity of the absorption bands is proportional to the irradiation dose. -centers occurs when the charge compensators have medium mobility. Lithium should give the best condition for color formation. Sodium (low mobility) and hydrogen (high mobility) should make smoky quartz colorless after heattreatment.

Infrared and chemical characterization of natural amethysts and prasiolites colored by irradiation

“…. The infrared spectrum of natural colorless quartz between 2400 and 4000 cm -1 is correlated to the potential of color development by irradiation and heating 16,17 . Bands related to hydroxyl between 3200 and 3600 cm -1 are influenced by the trace elements.…”

A new approach for spectroradiometric calibration consistency on the ground and in space

“…It became clear from earlier measurements of the effects of Co 60 gamma rays that natural fused silica impurities were producing a significant absorption by color centers in the ultraviolet. Gamma ray absorption effects on irradiated and heat-treated natural quartz effects are discussed in the paper by Nunes and Lameiras, 2005 [12]. The dimensions of the samples are 24 x 24 x 2.0 mm for the natural MSD and 24 x 27 x 2.0 mm for the synthetic MSD.…”

Comparison of bidirectional transmittance distribution function (BTDF) measurements on fused silica and sintered polytetrafluoroethylene diffusers

“…An excellent description of the composition and metrology of these basic materials is provided in Nurnberg, et al [28]. Changes in the optical absorption of natural fused quartz following gamma irradiation and heat treatment is presented in Nunes, et al [29]. Comparison of the directional hemispherical and bidirectional reflectance of both natural fused quartz and synthetic fused silica is provided in Heath and Georgiev [30].…”