The Internatsionalnaya pipe, also transliterated International or Internationalnaya, is a kimberlite diamond pipe in the Mirny district of Yakutia in the Russian Far East. It is part of the same Mirny kimberlite field that contains the famous Mir pipe, and it has long been recognised as one of the highest-grade diamond pipes in the world, although its absolute size is small compared with the giants of southern Africa.

Discovery and operation

The Internatsionalnaya pipe was discovered in 1969 during the systematic geological exploration of the Yakutian diamondiferous province that also yielded the Mir, Aikhal and Udachnaya pipes. Open-pit mining began in 1971, and the pipe transitioned to underground operation in 1999 once the surface ore had been worked out. The mine is operated by Alrosa, the Russian state-controlled diamond company that produces the bulk of the country's rough-diamond output and is one of the two largest diamond producers in the world by carat volume.

Grade and quality

What sets Internatsionalnaya apart is its grade. Published industry figures place the average grade at well over six carats per tonne of ore, an order of magnitude above most kimberlite pipes worldwide. The diamond population includes a high proportion of clean, well-formed crystals across a range of sizes, and the pipe has produced large stones, including specimens above 100 carats. Yakutian diamonds in general are noted for a relatively low frequency of strong fluorescence and for a colour distribution that yields a useful proportion of D to F colour stones.

Geological setting

The pipe is part of the Mirny kimberlite field, intruded into the Cambrian sedimentary cover of the Siberian craton. The kimberlite is of Devonian age, around 360 million years old, similar in age to several of the other major Yakutian pipes. The deep cratonic root of the Siberian shield is the source region for the diamonds, which travelled from the lithospheric mantle to the surface in the kimberlite eruption.

Trade significance

Internatsionalnaya output enters Alrosa's marketing channels and is sold through the company's regular sales process. The mine's high grade has made it a cornerstone of Alrosa's underground production, and its longevity has been extended several times by deeper mining levels. For the trade, a Yakutian provenance from the Mirny field is associated with reliable colour and clarity profiles in commercial sizes, although the rough is not generally marketed by individual pipe of origin once it enters polished circulation.