Sorting & valuation

In nature there are no perfect crystals, or two identical diamonds, so their grading involves sorting them by more than 8,000 criteria.

Each diamond crystal is described according to four major grading characteristics: weight (size), shape, defects (quality), and color.

However, no two diamonds are identical. In fact, grading diamonds can involve over 8,000 sorting criteria. All of the required expertise is available within ALROSA.

Here is a summary of the process.

Valuation stages and types of sorting

Preliminary valuation

Preliminary grading and sorting is carried out in our DiamondSortingCenter in Mirny, which receives all production from our ore treatment plants.

Initial valuation

Here we complete the process, by providing an assessment based on the RF Ministry of Finance price list.

The initial price of diamonds is determined in ALROSA’s United Selling Organization (USO) based in Moscow; at the Yakutsk Diamond Trading Enterprise in Yakutsk; and in the Kommeral Company in Mirny.

The largest (‘special’) diamonds

These are stones weighing 10.80 carats or more (diamonds of so-called ‘special’ sizes). We evaluate them using the RF Ministry of Finance method, which calculates a projected value for the polished diamond into which the rough stone may be cut. This valuation process involves computer simulation and modelling. Every stone is individually valued, then recorded in our integrated computer database.

Large diamonds

These are sorted manually, according to the classification system. Each stone is sorted visually by shape, clarity and color.

Medium and small diamonds

These are sorted using an expanded classification system. We use vibration tables to separate the mass of diamonds by shape, and an optical sorting system, SORTEX, to separate the diamonds by color. To certify the diamonds, and determine their value, we select a statistically representative sample. This is applied in accordance with the full classification system.

The smallest diamonds

These diamonds are used for industrial purposes, and are separated out at the preliminary sorting stage. They are then sent to the Kommeral Company, which sells industrial diamonds and manufactures diamond powders. Industrial diamonds of the boart (or bort) category, separated during the sorting process, are also sent to Kommeral.

ALROSA’s sorting system is certified by competent standardization bodies, and meets all relevant domestic and international standards.

How many carats?

The weight of a diamond is measured in carats. The word carat is derived from the name of the carob tree seed. This is because these reliably uniform seeds were traditionally used to measure the weight and volume of precious stones.

This page was last updated on 27 August 2013 at 14.05