Effect of Gamma Radiation Intensity on Color, Chemical Composition, and Crystal Structure of Prehnite

Abstract

Prehnite is a mineral used to make jewelry. Since most prehnite is light green and faded, this causes jewelry made from prehnite having low value. This research aimed to study the effect of gamma radiation intensity on the color, chemical composition, and crystal structure of prehnite before and after gamma irradiation. Fifteen prehnite samples were irradiated with gamma rays at intensities of 200, 400, 600, 800, and 1,000 kGy. The results revealed that after gamma irradiation, prehnite exhibited increased light absorption in the 300-400 nm wavelength range, resulting in a color change from light green to dark green and brown, depending on the increasing radiation intensity. The analysis of chemical composition by X-ray fluorescence (XRF) technique demonstrated that the main components of prehnite, including Ca, Si, Fe, and Al, remained unchanged before and after gamma irradiation. Iron was an important element involved in coloration. In this process, gamma irradiation oxidized Fe²⁺ into Fe³⁺, which created a color center, causing the prehnite to become darker brown. X-ray diffraction (XRD) analysis showed that the crystal structure of prehnite remained unchanged before and after gamma irradiation, retaining its orthorhombic crystal system with the space group P2cm. In conclusion, the gamma irradiation could alter the color of prehnite without affecting its chemical composition and crystal structure, which could be useful for adding value to prehnite in the gem and jewelry industry.