2023-08-01 17:32:02
Locations of the investigated gem minerals from Egypt and Saudi Arabia. Mineral scale photos of colored gems are given. – KHEDR ET AL.
MADRID, 1 Ago. (EUROPA PRESS) –
The unique elemental composition and atomic orientation of gemstones act as a ‘fingerprint’ that allows to discover the past of the stones and, with it, the historical commercial routes.
Researchers have used three modern spectroscopic techniques to rapidly analyze gems found in the Arab-Nubian Shield and compare them with similar gems from around the world.
In the study, published in the magazine ‘AIP Advances’the authors identified the elements that influence the color of the gems, differentiated the stones found inside and outside the region and distinguished the natural ones from the synthetic ones.
Since ancient times, gemstones have been mined and traded all over the world, sometimes traveling continents from their origin. Gemstones are geologically defined as minerals renowned for their beauty, strength, and rarity.
The team, led by Cairo University researcher Amal Abdelfattah Khedr, used three modern spectroscopic techniques to quickly analyze gems found in the Arab-Nubian Shield and compare them with similar gems from around the world. Using laser-induced decay spectroscopy (LIBS), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy, they identified the elements that influence gem color, they differentiated the stones found inside and outside the region and distinguished the natural ones from the synthetic ones.
The Arab-Nubian Shield is an exhibition of mineral deposits that intersperses the Red Sea in present-day Egypt and Saudi Arabia. Deposits date back to the earliest geological age on Earth, and precious metals and gemstones they have been mined for thousands of years.
“We show the main spectroscopic characteristics of the gemstones from these Near Eastern localities to distinguish them from their counterparts from other localities around the world,” explains Cairo University professor and co-author Adel Surour. “This includes a variety of gems of silicate, such as emerald from the ancient mines of Cleopatra in Egypt, as well as amethyst, peridot and amazonite from other historical sites, Most of which date from Roman times.
The different spectroscopic techniques they used revealed different information about the stones. LIBS quickly characterizes the chemical composition, while FTIR determines the functional groups related to the structure and indicates the presence of water and other hydrocarbons. Even for chemically identical materials, Raman spectroscopy shows the unique crystal structure of gem atoms.
The authors discovered that the iron content is related to the characteristic purple hue of amethysts, and that other elements such as copper, chromium, and vanadium are also responsible for the coloration. A distinctive water spout reveals lab-grown synthetic gemstones, useful for scientific purposes and identical to natural gemstones, but cheaper. Crystal structure differentiates amazonite beads from Mexico, Jordan and Egypt.
“Precious stones such as emerald and peridot have been mined since ancient times,” Surour explains. “Sometimes, some precious stones were taken by sailors and merchants to their countries of origin. For example, the royal crowns of Europe are decorated with peculiar gemstones that come from Africa or Asia We need precise methods to distinguish the provenance of a gemstone and trace the old trade routes to have correct information about the original place where it was extracted“, he states.
#analyze #precious #stones #discover #ancient #trade #routes