Gemology 101: Emeralds

The emerald may be a beryl, which we’re already delved into here, but as it’s the most famous of the family we felt it deserved its very own feature here on Sparkle Daily. Here’s a look at the prized stone and its interesting properties.

rough-emerald

What they are
Emerald is a variety of the mineral beryl, colored green by trace amounts of chromium and occasionally vanadium.

How they’re made
Most natural emeralds are made in hydrothermal veins – cracks in rocks deep within the earth which trap magma. Travelling with the magma are mineral deposits that, when the superheated fluid cools, crystallized and react with the minerals around them – forming emeralds and other gems. Emeralds are usually formed when the element beryllium combines with chromium. It’s chromium that gives an emerald its green color.

Their properties
Despite the emerald’s popularity as far back as Ancient Egypt – supposedly one of the first precious stones to be mined and fashioned by Ancient Egyptians – most emeralds are highly included. These inclusions are materials (in this case calcite deposits), trapped inside a mineral during formation, resulting in the stone’s poor resistance to breakage. Like other beryls, emeralds have a hardness of 7.5 – 8 on the Mohs scale.

In addition to numerous inclusions, emeralds are also susceptible to surface breaking fissures. Unlike diamonds which are graded by magnification, emeralds are graded by eye. If an emerald has no visible inclusions to the naked eye, it is considered flawless. However, it is important to note that stones with no surface breaking fissures are rare and so it has become common to treat all emeralds in a process called “oiling”. Cedar oil is often used in this generally accepted practice.

In an emerald, color is still paramount. Green beryls range in hue from a yellow-green to blue-green, but only gems that are medium to dark in tone are considered emerald. The finest emeralds, for example, are approximately 75% in tone on a scale where 0% is colorless and 100% is opaque black.

smooth-emerald

Where they’re found
Emeralds in antiquity were predominantly mined in Austria, India and Egypt – where the latter is generally accepted to be the world’s oldest source for the stone.

Today, Colombia is the world’s largest producer of emeralds, producing between 50% and 95% of the world’s emeralds. Zambia is considered the world’s second biggest producer of the stone, with Kagem Mines responsible for approximately 20% of the world’s emeralds. Emeralds are, however, found all over the world, including the US where deposits have been found in Nevada, Montana, Connecticut, North Carolina and South Carolina.

What to look out for
Because it is a well-known fact is that an emerald will almost always have visible inclusions, any emerald without inclusions is likely synthetic or an imitation.

Emeralds, like all colored gemstones, are graded using the four “Cs” – color, cut, clarity and crystal. Crystal refers to transparency. Normally, color is the most important factor in grading gemstones. In the grading of emeralds, crystal is considered a close second. A fine emerald must therefore possess a pure green hue as well as a high degree of transparency.

If this richly-hued stone has caught your eye, just as it has for others for centuries, why not consider purchasing your very own emerald jewelry? You can browse Jewlr’s range of emerald jewelry at jewlr.com/may-birthstone-jewelry.

(Images: rough emeraldsmooth emerald)

Where would you prefer to wear emeralds: on your ears, neck or fingers? Tell us below!

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