Russian diamond expert shares expertise with Canadians

Dr. Felix Kaminsky, director of the Moscow-based Institute of Diamonds, is justifiably proud of the diamond expertise established by Russian scientists during the latter half of this century.

In the past, these experts discussed advancements only in their own circle. But recent political changes have made it possible for Kaminsky and his colleagues to share information with people in the same field abroad. “We have much in common with Canada, now the hottest spot for diamond (exploration) in the world,” Kaminsky said. “You (Canadians) have good skills to prospect, good experience working in the North, and are famous around the world for techniques such as geophysics. We want to add to this the Russian diamond experience.”

Kaminsky was speaking at a recent diamond workshop in Vancouver, B.C., attended by The Northern Miner and a large crowd of Canadian explorationists. A veteran of the Russian diamond industry, he discussed methods for selecting prospective areas and revealed intriguing new discoveries of diamonds in rocks that cannot be classified as either kimberlites or lamproites. Diamonds are a $1-2 billion-per-year industry in Russia and thus rank high in economic importance. The former Soviet Union has four diamondiferous provinces and one off-craton diamondiferous belt. The most important of these, Yakutia (or Sakha), has the largest platform, Siberia, which encompasses 18 kimberlite fields.

Mining began in the late 1950s at the Mir pipe, but open-pit mining has ceased there and at some of the older mines as well, and preparations are now being made for underground mining to depths of 1 km. The operational problems at these older producers were underscored in 1992 when, according to De Beers Consolidated Mines, Russian production fell by 25%.

Mining has also stopped at Aikhal, which Kaminsky calls “the richest pipe,” as preparations are made for wider open-pit production. But operations are continuing at Sytykanskaya and at Udachny, the most important diamondiferous pipe in Russia. It is large and rich, with a huge processing plant. A more recently discovered pipe with large reserves, Yubileynaya, is in the startup phase of production.

The South Siberian province has alluvial diamonds, but so far only barren pipes have been found. Kaminsky believes more exploration in this region is warranted.

He also provided details of the Arkhangelsk diamond province in the Russian Platform. This diamond hunt, which began in the late 1960s, was based on the presence of garnets found in alkali-basaltic rocks.

“We bulk-sampled four of these alkali-basaltic pipes and found small diamond grains in two pipes,” Kaminsky said. “It was the first time diamonds were found in non-kimberlite rocks, as this occurred before the lamproite finds in Australia.”

These targets were not of economic importance, however, and efforts shifted 100 km to the east where traditional kimberlites were found by mineralogical and geophysical techniques. The first pipes proved to be barren, and the next had only a few diamonds. Eventually five kimberlites of economic interest were identified, and evaluations are continuing. “Foreign companies may be invited to participate in this project through a tender process this year or next,” Kaminsky said.

In 1989, Kaminsky was awarded the Order of Honor for his role in the discovery of the first diamonds in the Arkhangelsk region. It was challenging work for the geological team because the area was glaciated and covered by 30-70 metres of sediments and up to 200 metres of till.

The Arkhangelsk pipes are kimberlites, although Kaminsky said some minor evidence of lamproitic composition was noticed. It was also observed that they differed in minor ways from kimberlites in Yakutia; the Arkhangelsk pipes were well-preserved, with only a few tens of metres eroded, whereas, in Yakutia, some pipes have only small amounts of crater facies. The diamonds also differ. Yakutian macrodiamonds of both peridotitic and the rarer eclogitic paragenesis are characterized by multiple growth histories. It is common to find unresorbed octahedral external forms and non-octahedral cores (resorbed).

“At Arkhangelsk, we found, for the first time, two generations of diamonds,” Kaminsky said.

Arkhangelsk macrodiamonds contain well-formed octahedral cores overgrown by diamond of resorbed external form. But the microdiamonds are another story, in that well-formed octahedra predominate.

“The pipes are not as rich as the richest pipes in Yakutia, but (they are) about the same as (those in) South Africa,” Kaminsky said. “With up to 60% gems, the value is more than average and it may be economical for these pipes to be mined. It may be possible to produce several millions of carats per year at Arkhangelsk.”

The diamond search spread to other parts of the former Soviet Union, including Ukraine (part of the East European Platform). Four classic kimberlite pipes with G10 garnets were found in the Azov area, but these proved to be barren.

Some attention was also focused on the Urals, an off-craton diamondiferous belt where alluvial diamonds were first discovered in the 1820s. Although this region accounts for less than 1% of all Russian production, the alluvial diamonds discovered there are highly prized for their beauty and, therefore, almost never sold. “They are such perfect diamonds it is hard to imagine,” Kaminsky said.

He and other experts have researched many unusual sources of diamonds, largely in response to interest triggered by reports of diamonds found at the turn of the century in ultramafic rocks of British Columbia’s Tulameen district. While the validity of that discovery has been questioned, Kaminsky and his colleagues recognized and studied non-kimberlitic diamondiferous rocks in many diverse locales in the former Soviet Union and abroad. One of the more interesting finds was in Kazakhstan, where diamonds were found by chance in titanium-rich placers. They were small green cubes with elongated edges. Subsequent prospecting established primary sources, with some samples enormously rich in diamonds.

“It is now possible to calculate reserves in the billions of carats,” Kaminsky said. “But they are small (200-500 microns) and (entirely) of industrial quality. However, they have good abrasive properties and may have enough economic value to be mined.”

Kaminsky said this unusual diamond deposit is the only reliable find within regionally metamorphosed rocks. The genesis of these diamonds is still an enigma, although Russian scientists have proposed several theories. Another unusual find, of even higher grade, was made in northern Siberia, where diamonds are believed to have been formed from graphite by shock metamorphism caused by meteor impact. These aggregates of polycrystalline micro-metre-size diamonds are reported to have characteristics different from those of monocrystalline diamond.

The diamonds here are small (50 microns) and entirely of industrial quality, but Kaminsky said this impactite deposit might still be mined were it not for its remoteness. “These diamonds are more hard and more resistant to high temperature than diamonds from regular kimberlites and may be valuable in this sense,” he added.

He proceeded to discuss other unusual diamond discoveries worldwide, most of which have been found in off-craton settings. These include diamonds related to ultramafic bodies and those associated with platinum group elements, rather than the typical indicator minerals. So far, though, most of these non-traditional diamond finds are of academic, rather than economic, importance.

“I would not be surprised, however, if economic diamond deposits of the non-traditional type are one day found,” Kaminsky said.

His discussion of exploration techniques was of particular interest to the Canadian geologists in attendance. “We give large attention to prognostication, using geological, geophysical, mineralogical and morpho-structural techniques, because it is too expensive to prospect all our territory,” Kaminsky said.

In Yakutia, kimberlite fields are distributed linearly
and are related to zones of high permeability. Almost all bodies are within fault zones (normally twin faults) in places of intersection. The fields also have a morphological structure which is reflected in the topography, Kaminsky said. In the Arkhangelsk region (and elsewhere), the bodies exist along radial faults which have generally been discovered after the kimberlites. Russian diamond exploration also relies on advanced methods whereby barren and diamondiferous pipes can be differentiated without the need for drilling. These techniques are based on the chemical composition of indicator minerals associated with kimberlites.

“The Russian and South African methodologies are almost the same and were established at about the same time,” Kaminsky said. “The chromium-calcium ratio in G10 garnets was discovered over 20 years ago and has worked very well all over the world.”

Yet he became intrigued with the fact that some pipes were found with lots of G10s but with low grades. At Udachny (twin pipe), two types of kimberlite had the same amount of garnets, but one type was 10 times richer in grade than the other. And in South Africa a “zero pipe” was found which was filled with G10s but no diamonds.

In recent years, Kaminsky and Australian diamond expert William Griffin have begun researching this curious discrepancy using nickel thermometry and some Russian ideas on garnets. The objective was to devise a method for estimating grade that took into account both processes responsible for a pipe’s final grade — the positive process of diamond growth and the negative process of resorbing.

Proton microprobe analysis was focused not only on the main elements of the garnets but also on their minor or trace elements.

“The results were interesting and we hope to continue this research,” Kaminsky said. “It has possibilities to determine with greater confidence the possible grade of newly found kimberlite or lamproite.”

At present, South African and Canadian diamond experts study the composition of ilmenites as an indicator of resorption of diamonds within a specific pipe. In the past, advanced methods of prognostication were usually proprietary and developed by competing groups along independent lines. These days, however, South African, Russian and Australian techniques are being used in Canada, to the benefit of its fledgling diamond industry.

Donald Mustard, moderator of Kaminsky’s diamond workshop, said he welcomes today’s freer exchange of information and predicted Canadian geologists will soon rank highly among the world’s diamond experts. “The strength of Canadian exploration is the open society we have,” he said.