Achtaragdite (akhtarangite) is a mineralogical formation - a pseudomorphosis of a group of minerals (serpentinite, chlorite, grossular, as well as carbonates) after an unknown mineral of trigontritetrahedral appearance. It was discovered on the banks of the Vilyui River in 1790 by Academician E.G. Laksman. The world's second manifestation of akhtarandite was also discovered in Russia - in 2000.
You can see akhtarandite stone for sale and buy it in the Minerals of Russia online store.