May Birthstone

Emerald

EMERALD

As the birthstone for May, the emerald, a symbol of rebirth, is believed to grant the owner foresight, good fortune, and youth. Emerald, derived from the word smaragdus, meaning green in Greek, was mined in Egypt as early as 330 B.C. Today, most of the world’s emeralds are mined in Colombia, Brazil, Afghanistan, and Zambia. The availability of high-quality emerald is limited; consequently, treatments to improve clarity are performed regularly.

Emerald is a gemstone, and a variety of the mineral beryl (Be3Al2(SiO3)6) colored green by trace amounts of chromium and sometimes vanadium. Beryl has a hardness of 7.5–8 on the 10-point Mohs scale of mineral hardness. Most emeralds are highly included, so their toughness (resistance to breakage) is classified as generally poor.

Color

Scientifically speaking, color is divided into three components: hue, saturation and tone. Emeralds occur in hues ranging from yellow-green to blue-green, with the primary hue necessarily being green. Yellow and blue are the normal secondary hues found in emeralds. Only gems that are medium to dark in tone are considered emerald; light-toned gems are known instead by the species name green beryl. The finest emerald are approximately 75% tone on a scale where 0% tone would be colorless and 100% would be opaque black. In addition, a fine stone should be well saturated; the hue of an emerald should be bright (vivid). Gray is the normal saturation modifier or mask found in emerald; a grayish-green hue is a dull green hue.
Emeralds are green by definition (the name is derived from the Greek word "smaragdus", meaning green). Emeralds are the green variety of beryl, a mineral which comes in many other colors that are sometimes also used as gems, such as blue aquamarine, yellow heliodor, pink morganite and colorless goshenite.

Clarity

Emerald tends to have numerous inclusions and surface breaking fissures. Unlike diamond, where the loupe standard, i.e. 10× magnification, is used to grade clarity, emerald is graded by eye. Thus, if an emerald has no visible inclusions to the eye (assuming normal visual acuity) it is considered flawless. Stones that lack surface breaking fissures are extremely rare and therefore almost all emeralds are treated ("oiled", see below) to enhance the apparent clarity. Eye-clean stones of a vivid primary green hue (as described above) with no more than 15% of any secondary hue or combination (either blue or yellow) of a medium-dark tone command the highest prices. This relative crystal non-uniformity makes emeralds more likely than other gemstones to be cut into cabochons, rather than faceted shapes.

No comments:

Post a Comment