The gemstone associated with May is the emerald. Emeralds are a variety of the mineral beryl (Be3Al2(SiO3)6) colored green by trace amounts of chromium and sometimes vanadium. Beryl has a hardness of 7.5–8 on the Mohs scale. Most emeralds are highly included, so their toughness is fragile and they must be treated with care. These imperfections within the stone are unique to each emerald and can be used to identify a particular stone.
Emeralds are regarded as the traditional birthstone for May, as well as the traditional gemstone for the astrological signs of Taurus, Gemini and sometimes Cancer.
Emeralds in antiquity have been mined in Egypt since 1500 BCE, and India, and Austria since at least the 14th century CE.
Colombia is the world's largest producer of emeralds, constituting 50–95% of the world production.
Zambia is the world's second biggest producer, with its Kafubu River area deposits (Kagem Mines) anear Kitwe.
Emeralds are found all over the world in countries such as Afghanistan, Australia, Austria, Brazil, Bulgaria, Cambodia, Canada, China, Egypt, Ethiopia,France, Germany, India, Italy, Kazakhstan, Madagascar, Mozambique, Namibia, Nigeria, Norway, Pakistan, Russia, Somalia, South Africa, Spain,Switzerland, Tanzania, United States, Zambia, and Zimbabwe.