1. Emerald Variety of the Mineral Beryl
2. Grading of Emerald Gemstones
3. Article Photos
4. Emerald | Explore Our Collection
Emerald Variety of the Mineral Beryl
Emerald the distinctive and valuable gemstone is the green variety of the mineral beryl. Its unmistakable colour is caused by trace amounts of chromium and the chemical element vanadium. Flawless emeralds are incredibly rare and the vast majority are small, heavily included and feature surface reaching fissures and fractures which often cause the stone to break easily. For this reason many emeralds are treated to fill cracks and to improve clarity. Numerous treatments have been devised over the years in order to hide or disguise flaws and the finest grade gemstones can command staggering prices.
Although commercial grade emeralds are available worldwide in abundance, fine grade gemstones are extremely rare. The history of this grass green coloured stone can be traced back to Ancient Egypt and is known to have been mined as early as 1500 BC. The name comes from the Latin esmaralda/esmaraldus which was a variant of the Latin word smaragdus which originated in Ancient Greece. Smaragdos means green gem. Cleopatra loved emeralds and often covered herself in them during official occasions. Her palaces are believed to have been decorated with stones and having stated they were only fitting for Egyptian royalty, the emerald mines were made her personal possession. Her portrait was often engraved into larger stones which were then gifted to her favourite ambassadors.
National History Museum Los Angeles
Columbia mines more emeralds than any other country and most of the world's finest gemstones come from mines around Muzo which is known as the emerald capital of the world. The next largest producer is Zambia and a 5,655 carat emerald was found in October 2018 at Kagem which is the world's largest emerald mine.
Being lighter in weight than diamond and sapphire means that an emerald stone of the equivalent weight would be considerably larger. On Mohs scale of mineral hardness emerald grades 7½ to 8 so it's pretty hard but also very brittle. The hardness is often confused for toughness but the two characteristics are quite different. Mohs scale is a tool which measures the scratch resistance of one mineral against another.
During the Spanish conquest of Peru the invading Spaniards tested gemstones by means of grinding and pounding. During this process thousands of emeralds were destroyed because they were deemed worthless simply for being too soft.
National History Museum Los Angeles
Grading of Emerald Gemstones
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 close second followed by richness of colour, saturation and tone. Despite being the green variety of the mineral beryl not all green beryl is entitled to be called emerald. In order to qualify gemstones undergo rigorous testing during which the cut, shade and depth of colour, clarity and carat weight is assessed. Another interesting fact is that when assessing the clarity of a diamond, a loupe which is small powerful magnifier is used but when inspecting emerald gemstones it's generally done with the naked eye and if no visible inclusions can be seen, it will be classified as flawless.
The photos in this article are clickable and redirect to the original full size images. The exhibit at the top of the page is on display in the Smithsonian Museum of Natural History, Washington D.C (photo Stone Mania ©). The second two are in the Natural History Museum Los Angeles. Both photos are courtesy of Stan Celestian.