Emerald is the dark green to green-blue variety of the mineral beryl. The exact definition of emerald varies, and the level of intensity of the color for a gemstone to be defined as emerald is not strict, however, beryls that are light green are typically not considered emeralds.

Emerald's price is very high, due to its rarity. With a hardness of 7.5 to 8 on Mohs scale, it's one of the hardest gemstones. Nevertheless, it's also brittle, and a strong hit or extreme temperatures could make it crack, so it should be handled with care.

Color is another important factor that defines emerald's value: depending on the hue, color shade and saturation, emerald's price can vary widely. In general, the deeper and darker the color, the higher emerald's value is. Emeralds almost always have imperfections called inclusions, which make them appear less clear; clarity is another important factor that plays a role in grading emeralds and evaluating their price.

Most gemstone quality emeralds on the market come from Colombia. Additionally, there are emerald deposits in Zambia, China, Russia and the States, among others.