On the role of secondary electrons in the color change of high-dose X-ray irradiated topaz

TL;DR

This study explores how secondary electrons influence the color change in topaz when irradiated with high-dose X-ray beams, revealing new pathways for creating artificially colored gemstones.

Contribution

It demonstrates that lower energy X-ray beams can induce irreversible blue coloration in natural topaz, expanding methods for gemstone coloring beyond high-energy irradiation.

Findings

Secondary electrons play a key role in topaz color change.

Lower energy X-rays can produce permanent blue topaz.

New protocols for gemstone coloring are possible with controlled X-ray doses.

Abstract

Owing to its high brightness, synchrotron light allows for investigating with extreme precision the physical properties of matter. The irradiation with high-dose X-ray beams may also lead to modification of the latter, thus allowing for material processing. Here we investigate the color change of topaz irradiated with synchrotron light, shedding light on the role played by secondary electrons in the formation of color centers. As a matter of fact, treatments of natural topaz to induce its color change are largely used in the jewelry industry. Nevertheless, the physical mechanisms behind the topaz's color change have not yet been fully understood. To date, it has been shown that the combined action of high-energy beam irradiation (either electrons, neutrons, or {\gamma}-rays) and thermal annealing permits to provide colorless natural topaz with an artificial blue color, which is largely appealed in the gem market. Here we demonstrate that it is possible to irreversibly provide natural topaz with a blue color even by exploiting lower energy beams, such as X-rays, provided that enough dose is absorbed, thus paving the way for developing novel protocols for making artificially blue topazes.