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Pros and cons of extraterrestrial diamonds

21 september 2012

(m.interfax.by) - The vast reserves of impact diamonds* contained in the deposits located in Yakutia, the information of which was put into the public domain this week, do not claim to be a new Klondike ready to fill the market with rough diamond for many decades to come. There is such a wide abyss between diamonds of gem quality and impactites, which are unsuitable for cutting due to their unattractive appearance and small size, that experts jokingly say: if you want to part with your girl, give her an impact diamond. However, a certain part of minerals contained in the so-called Popigai Astrobleme may eventually take a decent niche in the market of industrial diamonds, without which the development of modern high-tech industries is just out of question.

In the opinion of Nikolai Pokhilenko, Director of the Institute of Geology and Mineralogy within the Siberian Branch of the Russian Academy of Sciences (RAS), who informed the public about the discovery, the new mineral could find wide application in the industry currently using industrial diamonds, both natural and synthetic. However, according to the spokesman of ALROSA (RTS: ALRS), which plans to study impactites together with the RAS, these diamonds are now more an object of scientific interest, and the talk about their market potential is premature.

Extraterrestrial diamonds ...

The Popigai Astrobleme (or meteorite crater) is located on the border of the Krasnoyarsk Region and Yakutia. "A space body fell into graphite rock. High temperature and pressure during the impact transformed graphite into dense carbon modifications, the main elements of which were regular cubic diamond having a lattice structure and lonsdaleite** having a hexagonal structure,” the ALROSA representative explained. “The resulting mineral is not exactly a diamond in its usual sense, it is an aggregate of different carbon phases, and essentially it is a nanosized composite, which is called impact diamond, for short."

In their appearance impact diamonds are very different from kimberlite diamonds. They usually take the form of narrow plates or needles with an average weight of 0.01-0.02 mg and average size of up to 2 mm; although there have been single crystals of a larger size, up to 12 mm. The content of this mineral in ore is not uniform, but in some areas it may be up to 300 carats per tonne. According to the Soviet data, total predicted resources exceed 100 billion carats.

As Nikolai Pohilenko told Interfax, there are no gem-quality diamonds in this area, so impactites cannot influence the state of the global diamond market. However, they could be used as an industrial raw material. In his opinion, due to the unique structure of impactites their technological characteristics (hardness and abrasive capacity) are 2 times better than those of high-quality industrial natural kimberlite or synthetic diamonds.

... whose superhardness is viewed differently

Abrasive qualities of impactites were discovered by Soviet geologists in the early 1970s at the early phase of exploration. The test trials at the Bakul Institute of Superhard Materials in Kiev proved that abrasion resistance of impact diamond powders was on average 1.5 times higher than that of similar powders made of natural and synthetic diamonds. This defined the basic direction of technological tests – they were aimed at cutting and grinding tools, as well as grinding powders.

The further tests in 1977 performed at the plants of the Ministry of Machine-Tool Industry of the USSR confirmed these findings. Durability and performance of impact diamond tools were two times higher compared with kimberlite diamond tools.

"If you use this stuff, you can increase labor efficiency in drilling, in manufacturing composite materials, in machining parts and ceramics, grinding, polishing, diamond cutting and optics,” Nikolai Pohilenko said. “Impactites may well compete with synthetic diamonds produced in China and Japan."

Meanwhile, according to Alexander Smelov, Director of the Diamond and Precious Metals Geology Institute of the Russian Academy of Sciences, the opinion of exceptional hardness of impactites is exaggerated, "because diamond itself has the highest hardness." "We can only speak of greater durability. In fact, impactites are just able to serve longer only on drill bits," he said.

Synthetic and industrial diamonds market

The question of whether there will be consumers for this new type of raw materials is no less interesting than the question of properties these minerals have. According to Bain, demand for industrial diamonds in 2010 completely correlated with supply and was about 4.5 billion carats. Now experts cite higher numbers (according to Nikolai Pohilenko, China alone is producing 7 billion carats).

At the same time, the share of natural minerals in the structure of production and consumption of "technical" diamonds is minimal - about 5%. The basis of this market is formed by synthetic diamonds globally produced since the 1950s. According to Bain, the largest manufacturer of synthetic diamonds is Element Six, which is part of De Beers and has factories in China, Europe and South Africa. Other important producers include Sumitomo Electric (Japan), Hehan Huanghe Whirlwind and Zhengzhou Sino-Crystal Diamond (China). Actually, China is currently turning out more than 90% of synthetic diamonds in the world.

Synthetic diamonds in this market have significant advantages over natural diamonds. They are cheap, and, in addition, the existing technologies make it possible to produce synthetic diamonds with properties that are needed by a particular consumer based on its needs - for example, it is possible to control their size, hardness, and thermal conductivity.

"It may be that impactites will be significantly more expensive than synthetic diamonds and even natural “technical” diamonds," the ALROSA representative told Interfax. “And then you may ask: Will be there consumer demand for expensive minerals, albeit having higher characteristics? Or will consumers prefer to buy several cheaper tools for the same money? To understand this, it is necessary to conduct extensive market research."

However, Nikolai Pohilenko is convinced that impactites can find a niche in the market. "The niche for natural industrial diamonds is very wide,” he said. “For instance, synthetic stones are not used in the automobile industry to manufacture internal combustion engines."

Mining prospects

The possibility to start mining impactites was already analyzed in the Soviet time. In parallel with the exploration domestic experts estimated the options for developing the deposit and even prepared technical and operational documentation. It envisaged the construction of a mining and concentrating mill powered by a nuclear unit, which could be built in the future, whereas finished goods could be transported by air.

However, over the years that geologists were working in these fields, the country built several plants to produce synthetic diamonds. Due to this impactites remained unclaimed, and their study was actually brought to a halt. The lack of infrastructure in the deposit area played a major role bringing about this decision.

There is also an open problem connected with the location of this deposit. "Popigay is seated on the 72nd parallel,” Alexander Smelov said. “And its development is extremely difficult due to severe environmental conditions."

"Popigay is nearly 200 kilometers north of Udachny,” the Interfax was told in ALROSA. "And, for comparison, further north than Norilsk. Right now there is no infrastructure in this area, and this, too, makes complicated any further study of the field and especially any plans for its development."

Placer impactites do not require beneficiation

In the 1970s semi-industrial diamond containing samples of impactites were studied by Yakutalmaz in Mirny. "The rock containing these crystals is very hard - so much that during the first test the crushing mill failed,” said the representative of ALROSA. "The extraction technique for impactites requires thermal dissolution, which is not economically viable these days."

"There are beneficiation problems with any ore,” Nikolai Pokhilenko agrees. “But now, having new technologies, the problem can be resolved. In addition, this area has alluvial deposits containing diamonds up to 6 carats per one cubic meter, and these minerals do not require beneficiation."

The data at the disposal of ALROSA also prove that placer occurrences of impactites appear promising for study. This is primarily the Sredne-Dogoyskaya Placer, where according to the evaluation work carried out the diamond grade reaches up to 3 carats per cubic meter (in some samples up to 30 carats per cubic meter), and predicted resources of this placer are estimated at 5.8 million carats. Other placer occurrences of impact diamonds in Yakutia are little studied.

According to the estimates made in 1999, the average price of impact diamond sized 0.5 mm from the above placers stood at $3.6 to $8.7. For comparison, the average price of one carat of diamonds produced by ALROSA is currently about $190.

Additional exploration prospects

Next year, the Institute of Geology and Mineralogy is going to send an expedition for additional exploration of impact diamonds found in the Popigai Astrobleme and their properties.

ALROSA will take part in this work. According to ALROSA, since 2013, the company is intent to work in team with the Russian Academy of Sciences to conduct scientific research on the properties of impactites and is now examining possible options for these works.

"The only thing that is clear today is that impact diamonds have been studied very insufficiently,” the representative of ALROSA said. "Their technological properties were studied at the level of the first half of the 1980s. Specifically, the reasons of their abrasive durability are not clear."

In addition, he said, it is necessary to study in detail their possible mining techniques, as well as perform a large-scale study of the industrial diamond market and demand for additional quantities of raw materials.

Perhaps in the process of research it will be possible to detect new technological properties of impact diamonds, which will make them useful for industrial purposes - for example, in the production of modern catalysts due to their chemical inertness. This will also be part of the proposed research. For now, the future of the Yakut "diamonds from space" buried in earth for 35 million years, appears vague and unclear, which is not surprising since their turn to be mined may only come if all other possible diamond reserves will be exhausted accompanied by a sudden collapse of the synthetic diamond industry.

* Impact diamonds - rock formed by collision of a meteorite with the Earth
** Lonsdaleite - substance similar to diamond, but having a different crystal lattice

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