Common alloying elements include&colon; manganese, nickel, chromium, molybdenum, boron, titanium, vanadium, tungsten, cobalt, and niobium. Vanadium's main application is in alloys, such as vanadium steel. These alloying ingredients include chromium, molybdenum, silicon, manganese, nickel and vanadium. Some black shales contain abundant heavy metals such as molybdenum, uranium, vanadium, and zinc. X multi-component alloy system where X represents chromium, tungsten, molybdenum, vanadium, or cobalt. However, during tempering, elements like chromium, vanadium, and molybdenum precipitate with the carbon. These contain other toxic metals, such as chromium, vanadium and cerium. It was also rich in asbestos, granite, vanadium, chromium and manganese. Copper, titanium, vanadium, and niobium are added for strengthening purposes. Emerald is green beryl, colored by trace amounts of chromium and sometimes vanadium. The Highveld is also exceedingly rich in diamonds, coal, vanadium, and manganese. Emerald derives its green coloring from either vanadium or chromium. It is the world's largest producer of chrome, manganese, platinum, vanadium and vermiculite. It is also used in processing aluminium, beryllium, copper, steel and vanadium. A large number of alloys of vanadium, nickel, and titanium absorb significant amounts of hydrogen.