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Tailing Dumps at the Malyshevskoye Emerald Deposit

31 july 2017

The tailing dump was started in the early 1960s during the development of the Malyshevsky and Aulsky quarries. When mining was over, the wastes (middlings) formed at the beneficiation plant, waste rocks and substandard ores from the Malyshevskaya mine were dumped there.

Two dumps were made: one for waste rocks and the other for substandard ores (poor in beryllium oxide).

The sampling results and their appraisal showed the following inferred resources:

- the ore content in the waste dump is 6 mln tonnes;

- crystal raw materials: emeralds – 9,154 kg, alexandrites - 294 kg, phenacites - 435 kg;

- the in-place reserves do not include the quantity of beryl that can be extracted and converted into the gem-quality raw materials using the up-to-date technologies.

It is an advantage that the ore-bearing rocks has already been unearthed to the surface and is ready to be processed.

As in the calculation of reserves, the extraction of crystal raw materials was carried out by crushing in a jaw crusher and a scrubber followed by handpicking, so in-place reserves show not the real content of the precious gem crystal raw material but its quantity actually extracted using the then existing methods.

In the early 1990s, an experiment was carried out to identify the beryl crystals labeled and placed in an sub-grade rock. After the crusher and scrubber, it was possible to find one half of a crystal and several small debris from 8 crystals. In total, about 12% of the initial amount.

Another example: the in-place reserves of emeralds in the waste dumps are 9,154 kg, and those of alexandrites are 294 kg. But according to the statistics related to the field, as per the data of GRP ‘Uralkvartssamotsvety’, the alexandrites account for up to 10% of the emeralds. That means they should be 915 kg.

It is the low efficiency of the existing methods used to extract the precious gems from the host rocks that were the main reason for the active search of alternative methods. Many various ways of crushing a host rock were studied – from hydrofracturing using high-pressure water jets to hydraulic impact techniques. After all, all the methods based on the rock destruction of the host rocks have one disadvantage: the minerals to be extracted are also crushed.

The first efforts to dissolve the host rocks were not successful because of chemical problems and the physical crystal disintegration due to Rehbinder effect. In spite of the fundamental unavoidability of the Rehbinder effect, the decision was taken to focus mainly on dissolving. Over several years of experiments, such chemical agents were found and procedures for their use were developed that allow the extraction of precious gems without losses, preserving 100% of their size, shape and weight.  

These studies resulted in the following procedure.

At the very beginning of the beneficiation process, it is necessary to refuse from crushing the rocks. Crushing is used just to see what is inside the piece of rock. In all the cases of interest to us, we are looking for a beryl-containing mineral inside the piece of rock. But beryl can be diagnosed using a beryllometer without opening a host rock. This can be done automatically and much faster than doing it manually. It ensures 100 percent accuracy.

On top of that, since the beryllometer is based on radiation effects, the personnel cannot be present during the sorting process. It also means that no theft is possible at this stage. After the initial sorting, the waste rocks go to the dumps, and the ore containing crystal raw materials is packed into containers (that can be closed automatically) and is transferred to the storage.

Further, when the rocks are obtained that definitely contain crystal raw materials in each piece of a rock it is not necessary to crush those rocks to extract the crystal raw materials. It is much more practical to use the proven procedure to dissolve the host rocks and select the precious gem crystals that remained undamaged.

During the dissolving process, the personnel has no contact with raw materials, and this also prevents any theft.

Rare elements can be extracted from the spent solutions. It is easy and cheap as they would be already dissolved.

The raw materials obtained are sorted, sized, if necessary, cut or used to produce souvenir minerals.

On the basis of the waste dump processing, it is possible to set up a mineralogical and local lore tourism. In addition to tourism, it is possible to sell minerals specimens - both those from the concentrated raw material storage and ready-made ones produced at the factory. There are also great opportunities to make mineral collections: for amateurs, schools and academic institutions – collections can be of any level of complexity.  

To sum up the technological part:

1. Identification of the beryl-containing crystal raw material in the source rock.

2. Storage of ore containing crystal raw material.

3. Ore goes from the storage to the dissolution workshop.

4. The extracted crystal raw material undergoes sorting as follows:

4a) fit for cutting;

4b) fit for sizing and cutting, if necessary;

4c) fit for color improvement/modification to remove 'beryl’ grey-yellow hues and make green and blue main colors more intensive, and then – for sizing and cutting.

Additional technological equipment

The standard equipment for loading, transportation and classification of the mined rocks can be added: a sorting machine with radiative light and the equipment for dissolving the host rocks.

Sorting lines for crystal raw material during the dissolution process can also be added, for sorting the selected crystal raw material, as well as for sorting the treated raw material (color improvement, sizing, etc.). Radiation ‘backlighting’ is only necessary for the initial sorting of the incoming ore. The rest sorting lines use conventional lighters.

The equipment for the raw material treatment (color improvement, sizing, etc.) can be added as well.

What are the expected results?

While processing the waste dumps, it makes sense to expect exactly that quantity of crystal raw material that was specified in the inferred resources.

Using the existing technologies, there is no doubt that these quantities can be achieved, because the reserves were calculated using this very existing technological process comprising the crusher, scrubber and manual sampling. However, calculations can be made in a different way.

For example, the quantity of beryl stones is 100 times more than that of emeralds. It means that for every tonne of emeralds there are 100 tonnes of beryl stones, with 25% being the green beryl of various grades. The experiments carried out showed that up to 20% of the green beryls turn into emeralds after treatment. It makes 5 tonnes of additional emeralds per one tonne of the approved reserves.

Moreover, about 70% of the remaining 80% of green beryls have a ‘beryl’ hue that significantly decreased their value – it can even exclude them from the commercial turnover. After improving the color and transparency, the average price of the green beryl stones is up to $100-plus and even up to $1,000 per one kilogramme. With the average price for the emeralds of $10/gr, the beryl price of $1/gr with the 20 tonnes available gives additional twofold sum to the value of the raw material mined. So, just due to improving the color and transparency, the value of the emerald and beryl raw materials increases by 8 times.

Unfortunately, it is not possible to accurately compare the yields of the crystal raw material during crushing and dissolving of the source rock. For obvious reasons, these experiments could not be carried out. However, by indirect evidence and based on the practical experience to date, it is possible to tell that in case of dissolving method the yield of the crystal raw material is at least two times higher than when crushing is used. without carrying out large-scale work it is not possible accurately take into account many important nuances influencing the cost of the ready products, such as the increase in the average size and weight of the raw material pieces and cut stones, color and transparency improvement and commercial use of the raw materials with various decorative features like ‘moonshine’ effect, Venus hairstones, aventurescence, ‘cat’s eye’ effect, etc.

But even taking into account the improvement of transparency and color enhancement in the treatment of emeralds and beryls, we finally get a 30-fold increase in the cost of extracted crystal raw material in comparison with the forecast one.

New technologies make it possible to manufacture various unique products that cannot be made with the current technology. The controlled dissolving of the run-of-mine ore also enables to extract mineral samples from the ore and make souvenir products. Their cost fully covers the expenses for the whole cycle of the crystal raw material production. It means that it allows to arrange the systematic operation of the enterprise and not hope for any occasional lucky discovery of very expensive crystals.

Legislation

As per the current russian legislation:

Under the effective Russian legislation, the treatment within the framework of the declared technological process - up to the final sorting and evaluation - is quite possible, but under the mining license only. The sale of the sorted-out and evaluated raw emeralds and alexandrites is only possible if the buyer is registered at the Assay Chamber.

It is not allowed to sell not open mineral samples;

It is not allowed to sell not open emeralds, alexandrites in the rock;

It is not allowed to sell mineral samples of emeralds, alexandrites;

It is not allowed to sell souvenir products containing precious stones.

It must be noted that the quantity of the alexandrite stones obtained as a result of dissolving the ore is hundred times higher than when using crushing. And it also ensures that the stone is practically not damaged. The Malyshevskoye deposit has a global monopoly on this product. So, the financial component of this statutory bar is rather significant.                                                                                                                                                                

The price for a small-size alexandrite stone (non-gem quality) starts from several hundred dollars. The value of unique stones can be higher - up to hundreds of thousands of dollars. Due to great rarity of alexandrite on the world market, the cost of a raw material stone in an intact rock is much higher than that of a crushed gem quality raw material or a cut stud. While alexandrites are found in insignificant quantities in several deposits in the world, the combination of an alexandrite and an emerald or a phenacite in one stone does not occur anywhere else in the world. And these are not uncommon at the Malyshevskoye field.

The situation with the sale of collections is vague. It is possible to sell collections without precious gems, but the price would be lower. It is not possible to sell collections with the precious gems. It is not allowed to sell the mineral collections to foreigners as this is governed by the state secret regulations. And how to differentiate them?

Alexander Bogolyubov, Viktor Bogolyubov and Oleg Sharovatov

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