Jet is a mineral-like material derived from decaying wood placed under extreme pressure. Owing to its organic origins the chemical composition of jet varies and therefore like amber, cannot be classified as a mineral. Jet is either black or dark brown in color.
Jet is easily polished and is used in manufacturing jewellery. Jet as a gem material was popular during the reign of Queen Victoria, during which the Queen wore Whitby jet as part of her mourning attire.