Emerald is a gemstone or precious stone that is green to dark green in color. Emerald is a beryl silicate mineral & x28;contains beryllium& x29; and its green color is caused by chromium traces. The presence of vanadium and iron that accompanies chromium traces will cause the various zones of the green color. Emerald has a high hardness & x28;7.5 on the Mohs scale& x29;.