These treatments are typically applied in a vacuum chamber under mild heat, to open the pores of the stone and allow the fracture-filling agent to be absorbed more effectively. The least expensive emeralds are often treated with epoxy resins, which are effective for filling stones with many fractures. Other liquids, including synthetic oils and polymers with refractive indexes close to that of emeralds, such as Opticon, are also used. Cedar oil, having a similar refractive index, is often used in this widely adopted practice. Most emeralds are oiled as part of the post- lapidary process, in order to fill in surface-reaching cracks so that clarity and stability are improved. Faceted emeralds are most commonly given an oval cut, or the signature emerald cut, a rectangular cut with facets around the top edge.
The relative non-uniformity motivates the cutting of emeralds in cabochon form, rather than faceted shapes. 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. Imperfections are unique for each emerald and can be used to identify a particular stone. The inclusions and fissures within an emerald are sometimes described as jardin (French for garden), because of their mossy appearance. Stones that lack surface breaking fissures are extremely rare and therefore almost all emeralds are treated ("oiled", see below) to enhance the apparent clarity. Thus, if an emerald has no visible inclusions to the eye (assuming normal visual acuity) it is considered flawless. 10× magnification, is used to grade clarity, emeralds are graded by eye. Unlike diamonds, where the loupe standard, i.e. Įmeralds tend to have numerous inclusions and surface-breaking fissures. Clarity Brazilian emerald (grass-green variety of the mineral beryl) in a quartz-pegmatite matrix with typical hexagonal, prismatic crystals. Gray is the normal saturation modifier or mask found in emeralds a grayish-green hue is a dull-green hue. In addition, a fine emerald will be saturated and have a hue that is bright (vivid). The finest emeralds are approximately 75% tone on a scale where 0% tone is colorless and 100% is opaque black. Only gems that are medium to dark in tone are considered emeralds light-toned gems are known instead by the species name green beryl. Yellow and blue are the normal secondary hues found in emeralds. Emeralds occur in hues ranging from yellow-green to blue-green, with the primary hue necessarily being green. In gemology, color is divided into three components: hue, saturation, and tone. In America, the distinction between traditional emeralds and the new vanadium kind is often reflected in the use of terms such as "Colombian emerald". As a result, vanadium emeralds purchased as emeralds in the United States are not recognized as such in the United Kingdom and Europe. In the 1960s, the American jewelry industry changed the definition of emerald to include the green vanadium-bearing beryl. This member of the beryl family ranks among the traditional "big four" gems along with diamonds, rubies and sapphires. A fine emerald must possess not only a pure verdant green hue as described below, but also a high degree of transparency to be considered a top gemstone. However, in the grading of emeralds, clarity is considered a close second. Normally, in the grading of colored gemstones, color is by far the most important criterion. Properties determining value Cut emeraldsĮmeralds, like all colored gemstones, are graded using four basic parameters known as "the four Cs": color, clarity, cut and carat weight. According to Webster's Dictionary the term emerald was first used in the 14th century. The word "emerald" is derived (via Old French: esmeraude and Middle English: emeraude), from Vulgar Latin: esmaralda/ esmaraldus, a variant of Latin smaragdus, which was via Ancient Greek: σμάραγδος (smáragdos "green gem") from a Semitic language. Most emeralds have lots of material trapped inside during the gem's formation, so their toughness (resistance to breakage) is classified as generally poor. Beryl has a hardness of 7.5–8 on the Mohs scale. None (some fracture-filling materials used to improve emerald's clarity do fluoresce, but the stone itself does not)Įmerald is a gemstone and a variety of the mineral beryl (Be 3Al 2(SiO 3) 6) colored green by trace amounts of chromium or sometimes vanadium. Hexagonal (6/m 2/m 2/m) Space group: P6/mсc
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