The word “emerald” comes from smaragdos, the ancient Greek term for a green gem. Roman author Pliny the Elder, who died during the 79 CE eruption of Mt. Vesuvius, wrote in his encyclopedic Natural History that “nothing greens greener.”

People have loved emeralds for millennia, associating them with rebirth and renewal. As May’s birthstone, emerald defines the colour green—from Ireland’s poetic nickname “the Emerald Isle” to the gemstone’s vibrant hue.

Legend says emeralds boost intelligence and quick wit, and people once believed they could cure diseases like cholera and malaria. Today, the gemstone marks the 20th and 35th wedding anniversaries.

While pure emeralds are colourless, impurities often tint them green, blue, yellow, pink, or red—the rarest. The green colour comes from trace amounts of chromium or sometimes vanadium.

Beryl has a hardness of 7.5–8 on the Mohs scale.  Emerald isn’t well suited to everyday wear, such as engagement rings due to it being soft and brittle.

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.

Collectors prize emeralds that offer high transparency and evenly distributed colour without visible zoning. If the hue leans too yellow or too blue, the stone isn’t an emerald but another type of beryl, which lowers its value.

People often link an emerald’s appearance to its mine location. Colombian emeralds tend to show a warmer, more intense pure green, while Zambian emeralds lean cooler with a bluish-green tint. Despite these generalizations, emerald appearances often overlap across sources.

Emeralds usually contain inclusions visible to the naked eye, and the presence of these inclusions is accepted. Unlike diamonds, which graders examine under 10× magnification, experts grade emeralds by eye. If an emerald shows no visible inclusions, it earns a flawless rating—and because eye-clean emeralds are rare, they hold tremendous value.

To improve clarity, gemologists sometimes fill inclusions with oils, waxes, or artificial resins to reduce their visibility. These fillers vary in stability, and the amount used can range from minimal to significant. However, filled emeralds can suffer damage from exposure to hot water and detergents during cleaning.

Emeralds belong to the mineral family beryl, prized for their unique green beauty.