AsianScientist (Mar. 16, 2016) – Researchers from India have tested an unusual way to improve the color, clarity and luster of rubies: microwaves. The study was published in Applied Physics A.
Rubies are among the world’s most popular precious gemstones, and are also used in high power switches and sensors. Most natural rubies are not uniform in color, and sometimes blue patches can be seen in the red stone. This decreases the value of the stone.
Heat treatments such as high energy, lasers, applying different chemicals or surface coatings and particle or electron beam irradiation are some methods that have been used on rubies to improve color saturation, clarity and trading value. The research team at India’s Council of Scientific and Industrial Research (CSIR) Institute of Minerals and Materials Technology is the first to add microwave heating to the possible methods of treating red gemstones. This technique has already been successfully used for materials such as ceramics, metals and composites.
The researchers tested the technique on natural rubies collected from Sinapali in Odisha. These hexagonal prisms varied in size between 5-11 millimeters. The gemstones were placed in a basic 3 MW microwave furnace, and treated at 1,500°C. The team then used various techniques to investigate and compare the microwaved ruby samples with untreated ones. These include X-ray diffraction, ultraviolet-visible spectroscopy, fluorescence spectrophotometry, Raman spectroscopy and X-ray photoelectron spectroscopy.
It was found that the microwave treatment led to visible changes in the gemstones’ color, from reddish black to light pink, and structure. The researchers believe this subtle change in the stones’ surface color and increase in clarity may be caused by changes in the chromium, iron and titanium elements in the gems. Fewer defects, irregularities and impurities in the stones were also noted among others, because of changes in the atom layout and crystal structure.
“Microwave heating, an unconventional method of fast thermal excitation, produces new results in gemstones like rubies,” says study lead Subhashree Swain. “The study provides a new vista for future workers in the area.”
She adds that the use of microwave heating has many advantages for the gemstone industry. It is quicker than conventional heating and ensures uniform heating, which in turn can aid rapid product development. It is also an energy-saving and eco-friendly process.
The article can be found at: Swain et al. (2016) Microwave Heat Treatment of Natural ruby and its Characterization.
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Source: Springer; Photo: Peter Richardson/Flickr/CC.
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