Oltu stone aka black amber, a kind of jet
Oltu stone (Turkish: Oltu taşı) is a kind of jet found in the region around Oltu town within Erzurum Province, eastern Turkey. The organic
Jet
Jet is a type of lignite, the lowest rank of coal, and is a gemstone. Unlike many gemstones, jet is not a mineral, but is rather a mineraloid. It is derived from wood tha