Malachite is a copper carbonate with distinctive green veining. Though not a particularly hard stone, it takes an excellent polish. Malachite is usually found near copper ore deposits. The most famous malachite mines were in the Ural mountains in Russia, where 20 ton blocks were once taken from the quarries to decorate the palaces of the Russian tsars. Today malachite is a scarcer material and the most important producer is the Congo (formerly known as Zaire).​​