One of the five cardinal gems, Emerald is a gemstone and a variety of the mineral beryl. Beryl is a mineral composed of beryllium aluminium silicate with the chemical formula Be3Al2Si6O18. Well-known varieties of beryl include emerald and aquamarine.
The word “emerald” comes from smaragdos, ancient Greek for a green gem. Roman author Pliny the Elder, who died in the 79 CE eruption of Mt. Vesuvius, wrote in his encyclopedic Natural History that “nothing greens greener.
Emerald, the birthstone for May, has been beloved for millennia, evoking rebirth and renewal. Widely regarded as the definition of green. From the poetic description of Ireland as “the Emerald Isle” to the vibrant green of the famed gemstone itself.
Legend has it that emerald has the power to make its wearer more intelligent and quick-witted, and it was once believed to cure diseases like cholera and malaria. Today, it’s the gemstone given for the 20th and 35th wedding anniversaries.
Pure beryl is colourless, but it is frequently tinted by impurities; possible colours are green, blue, yellow, pink, and red (the rarest)
The colour green comes from trace amounts of chromium or sometimes vanadium.
Beryl has a hardness of 7.5–8 on the Mohs scale. It is a soft and brittle stone, that isn’t well suited to everyday wear, such as engagement rings.
The intensity of the green in the finest emeralds might not be equalled by anything else in nature.
The most desirable emerald colours are bluish-green to pure green, with vivid colour saturation and a tone that’s not too dark. The most prized emeralds are highly transparent. Their colour is evenly distributed, with no eye-visible colour zoning. If the hue is too yellowish or too bluish, the stone is not emerald, but a different variety of beryl, and its value drops accordingly.
Emerald appearance is sometimes associated with its mine location. Colombian emeralds are said to have a warmer and more intense pure green colour. Zambian emeralds are said to have a cooler, more bluish-green colour. Despite these theories, the truth is that emerald appearance overlaps between sources.
Emeralds typically contain inclusions that are visible to the unaided eye. Because of this, the presence of inclusions is excepted in emeralds.
Unlike diamonds, where the 10× magnification is used to grade clarity, emeralds are graded by eye. Thus, if an emerald has no visible inclusions to the eye it is considered flawless. Eye-clean emeralds are precious because they’re so rare. To improve the appearance of an emerald, inclusions are sometimes filled with oils, waxes, and “artificial resins” —to reduce the visibility of the inclusions and improve the apparent clarity. These substances have varying degrees of stability, and the volume of filler material present can range from insignificant to major amounts. Avoid exposure to heat, changes in air pressure (such as in an aeroplane), or chemicals. Filled emeralds can also be damaged by exposure to hot water and detergents used for washing.
