The World’s Largest Piece of Ural Malachite Turned 245 Years Old
A malachite block weighing a ton and a half was extracted from below the surface 245 years ago in the vicinity of the area where nowadays the town of Polevskoye, Ural, stands.
The lump of the mineral could have been even more massive, but due to the technical difficulties, the chunk could not pass through the narrow openings of the deposit. Consequently, mine workers had to be gradually cutting off small pieces of the rock until the malachite block could be pushed out of the working.
The lump of the most sought-after gem of the 18th century was gifted to Catherine the Great. The Empress of Russia kept the rock in her private collection and then handed the sample over to the Mining Museum, St. Petersburg.
The unique discovery remains so far a part of the Museum's collection; it is also acknowledged as the world's largest chunk of Ural malachite, which has survived up to the present day. The exhibit is not only rare but also highly valuable, with the price of the solid block estimated at several million US dollars. The ornamental stone is no longer extracted - Russian deposits are nearly depleted, whereas specimens mined in Africa are often of much lower quality.
Malachite is a copper carbonate hydroxide mineral. If the stone's sample is heated up to 200 degrees, it will turn black and change into the form of a copper oxide powder. Turning the powder back into the rock - that is, malachite - is an impossible task.