Our process

Stage 1Mining

Open-pit mining operations

ALROSA uses advanced machinery in all our open-pit mines. These include excavators, drill rigs, and loaders, of both Russian and foreign makes. To prevent diamond breakage when blasting rock, we use special low-impact technology. In fact, our pits are unique. In terms of both mining practice and geological parameters, they are unmatched anywhere in the world.

After the open pit reaches the planned design depth, the area of mining operations is expanded.

The ore (kimberlite) is extracted by blasting, then transported to a processing plant by supersize mine trucks (with a capacity of up to 136 tonnes).

Underground mining

An ALROSA underground mine is comprised of many kilometers of shafts and horizontal mine workings, shaft stations, compressor units that pump air under the ground, refrigerating plants that bind the host rock, and other powerful machinery and equipment, including supersize load-haul-dump vehicles (LHDs) and continuous mining systems. And the surface facilities of an underground mine consist of a good dozen of buildings.

Down in the mine face they begin with cutting stopes enabling the operation of continuous mining systems. After the ore is extracted, the empty spaces are filled with specially prepared backfill mix.

The ore that is drawn to the surface is then transported to a processing plant by mine trucks.

Stage 2Ore Treatment and Concentration

Ore reduction (comminution), wet autogenous milling

After coarse reduction in jaw or cone crushers the diamond-bearing ore is fed into drum mills for wet milling. Lumps of ore of up to 1.5 metres in size are reduced to 0.5 metres and smaller.

This slurry of finely ground ore is sent into spiral classifiers, separating the material by density.

The ore is then screened into several fractions. After that, each fraction is processed separately.

Froth flotation, dense media separation (DMS)

Mid-sized material is processed in jigging machines and dense media separation (DMS) units. Pulsating water jets separate the diamonds from the slurry. Smaller-sized material, together with water-soluble flotation agents, go into a froth flotation machine where small-size diamonds stick to froth bubbles, and are carried to the final concentration stage.

X-ray Fluorescent Separation

Large-size material is processed by X-ray fluorescent separation (based on the principle that diamonds fluoresce in X-rays).

The diamond-bearing concentrate is X-rayed while moving along the trough of the separator. After detecting a flash caused by fluorescence, a special tool cuts precious gems away from the waste rock.

In the final recovery unit, diamonds are cleaned, sieved, handpicked, roughly sorted, and packed into containers.

Stage 3Diamond sorting and marketing

Preliminary sorting and valuation

Rough diamonds, originating from different ALROSA mines in Yakutia, are transported to Mirny. Here they are given a preliminary sorting into size categories, and also receive a preliminary valuation. At this stage, we also monitor the output from our various mines – this helps with future production planning.

Next, the diamonds are sent to our United Selling Organization (USO) in Moscow.

Sorting is arranged by strict reference to master samples of gem quality and color. All stones are classified into 16 size and weight categories, according to international standards.

Valuation and sales

As explained, the final sorting and valuation of rough stones is carried out in our United Selling Organization (USO).

Diamonds in the large size and weight categories are exclusively hand sorted. To sort medium and small stones, we use vibration tables (to sort by weight) and optical systems (for colour). At this point of pre-sale preparation, diamonds from different mines are mixed and boxed by categories. We then sell rough stones to Russian-resident and foreign-based diamond manufacturers and wholesalers, both under long-term contracts, and also by tender.

Stage 4Diamond manufacturing techniques

Our techniques

Diamond manufacturing techniques include planning (or marking), sawing, bruting, faceting and polishing. Most operations are manual. Robots and semi-automatic machines are only used for manufacturing cheaper and smaller diamonds.

Our Moscow-based Brillianty ALROSA (ALROSA Brilliants) cutting and polishing division produces stones of 4-6 grams and above. These are cut and polished into round or fancy shapes, across the entire range of size and weight categories.

Smaller stones are cut and polished at ALROSA subsidiaries in Central Russia, in Barnaul and Orel.