January 30
Siberian geologists have explained the origin of unusual yellow diamonds
Most of the diamond deposits in Russia are located on the territory of the Republic of Sakha (Yakutia). The north of this region is known for rich diamond-bearing placers, the root source of which has not yet been found, despite the large volume of previous geological exploration work. Scientists of the Institute of Geology and Mineralogy of the SB RAS and Novosibirsk State University have conducted a comprehensive study of diamonds to help industrial companies in search of an unknown deposit.
The results of the research are published in the special issue of the authoritative scientific journal Lithos. The first author of the article, the professor of the Russian Academy of Sciences, doctor of geological and mineralogical sciences Dmitry Zedgenizov told about it. He is also the leading scientific employee of the laboratory of experimental geochemistry and petrology of the Earth's mantle GGF NSU, who is currently a member of the SAU NSU named «Geological and geophysical research in the Arctic and global priorities».

— Diamond is a unique material. For us, scientists, diamonds have a huge scientific value, no less than diamonds for "high society." The fact that diamonds are formed at a very great depth, of 150-250 km (there are deeper). On the surface, they are carried out by specific kimberlite magmas, which are formed at a corresponding depth. Of course, it is impossible to drill well at such a distance, and thus, when studying diamonds, we evaluate the composition, structure, and evolution of those deep parts of the Earth, to which we cannot reach in any other ways, says Dmitry Alexandrovich.

— Our work is devoted to the study of diamonds from the placers of the northern regions of the Yakut diamond-bearing province, where can be found a specific variety of yellow diamonds. They are not very similar to those crystals that we used to imagine ourselves: a beautiful shiny transparent octahedron. These diamonds are round-curved crystals, they have a cubic form and a bright yellow color (yellow-green and dark orange were also found), says the geologist.

After a necessary processing, diamonds they often have additional value, because there are not so many yellow gems in the world. So, for example, the cost of some intensely yellow diamonds sold at Sotheby's and Christie's auctions reaches hundreds of thousands of dollars per carat. The main Russian diamond-mining company also notes an increase in demand for yellow rough diamonds. The largest diamonds are given names, and they are deposited in the Diamond Fund of the Russian Federation.

— Why we took up the study of these diamonds? Primarily because of very limited study data. On this basis, the interpretation of their origin requires further adjustment. Secondly, the root origin of diamonds

from placers, including yellow diamonds is still not known. Thus, by studying such diamonds, we, scientists, create a scientific and methodological basis for diamond prospecting, — explains Dmitry Alexandrovich.

— It is known that diamonds get their yellow color due to the presence of single nitrogen atoms (so-called non-aggregated nitrogen defects) in the diamond structure. They indicate that these diamonds before they were carried to the surface, were in the mantle in very cold conditions for extremely short (on a geological scale), a period of time. Therefore, there is a need for a detailed study of yellow diamonds, at least for understanding in what specific conditions and in which part of the mantle they formed.

Based on the complex study, the geologists concluded that the yellow diamonds probably have crystallized from the remains of organic matter (the remains of living organisms), once located on the surface of the Earth as part of an ancient oceanic plate.

— There is an industrial development of these placers of the northern regions of the Yakut diamond province, a subsidiary of ALROSA «Almazy Anabara». The main task for geologists from mining companies, with whom we are actively working together, is to search for the indigenous deposits, that underwater canal which helps these diamonds to appear at the surface.