Emerald is a highly sought after precious gemstone that's a green variety of the mineral beryl. Its unmistakable rich green colour is caused by trace amounts of chromium and the chemical element vanadium. Flawless stones are incredibly rare and the vast majority of emerads are small, heavily included and feature surface reaching fissures and fractures which lower the stone's resistance to breakage. For this reason most emeralds are treated in order to fill cracks and improve clarity. Numerous treatments have been devised over the years in order to hide or disguise flaws and the finest grade emeralds can command staggering prices.
Although commercial grade stones are available in great abundance, the finest material is extremely rare. Emerald is one of the most highly prized of all gemstones not only because of its magnificent colour but also because of its brilliance (light reflected from the interior of the stone) which is far superior than that of any other green gemstone.
Emeralds tend to be small and lighter in weight than diamond or sapphire which means a one carat stone will also be considerably larger. Columbia mines more emeralds than any other country in the world and some of the finest specimens come from the mines around Muzo which is known as the emerald capital of the world. During the Spanish conquest of Peru the invading Spaniards tested stones by grinding and pounding them and thousands of emeralds were destroyed because they were deemed to be worthless simply because they were softer than diamonds and sapphires.
Several characteristics are taken into consideration when grading coloured gemstones but colour is generally the most important. Having said that, with emeralds clarity comes a very close second followed by richness of colour, saturation and tone. Even though emerald is the green variety of the mineral beryl, not all green beryl is entitled to be called emerald. In order for a gemstone to qualify it undergoes rigorous testing during which the cut, shade and depth of colour and clarity and carat weight is assessed. Another interesting fact is that when assessing the clarity of a diamond a loupe (small powerful magnifier) is used but when inspecting an emerald, it's generally done with the naked eye and if no visible inclusions can be seen, it will be classified as flawless.
Emeralds were mined in Ancient Egypt as early as 1500 BC, the mines are said to have belonged to Cleopatra who loved these stones and often had her portrait engraved upon them. The emeralds worn by the Romans are said to have come from Cleopatra's mines
Columbia and Zambia are currently the world's largest producers of emerald although stones can be found worldwide. A 5,655 carat emerald was found in October 2018 at Kagem, the world's largest emerald mine. It has been named Inkalamu which means lion in the local Bemba language.
Despite being graded 7½ to 8 on Mohs scale which is relatively hard for a gemstone, emerald is brittle hence will break easily.