Emerald
Emerald is the recommended stone to give for a twentieth or thirty-fifth wedding anniversary and is May's birthstone. It is the green variety of the mineral beryl and one of the most highly prized of all the gems. The name Emerald is from the Greek "smaragdos" (green stone), through the Latin "smaragdus" to Middle English "esmeralde." Aside from being the birthstone for May, it was historically believed to bestow on its wearer faithfulness and unchanging love. According to legend, the wearing of emerald not only cured a wide range of ailments, including low I.Q., poor eyesight and infertility, but also enabled the wearer to predict the future. As a revealer of truth, this gem was an enemy of all enchantments and conjurations. It was therefore greatly feared by magicians, who found all their arts of no avail if an Emerald were in their vicinity when they began to weave their spells. However those caught by Cupid's bow found the gemstone useful in learning the truth or falsehood behind the oaths of their lovers. The Emerald has also been worn or utilized in magic for protection. The stone was bound to the left arm with string to guard travelers. They were given to "possessed" persons to exorcise the evil entity within them. Emeralds were employed as an antidote for poisons and for poisoned wounds. To gaze into an Emerald was said to increase sight and relieve eye strain.
The finest quality emerald has the color of fresh young green grass, an almost pure spectral green, possibly with a very faint tint of blue, as in the "drop of oil" emerald from Colombia, which is considered to be the world's finest. Its fine intense green coloring is due to a trace of chromium or vanadium replacing the aluminum in the beryl structure. Because of the nature of this replacement, almost no Emeralds with intense color are free from inclusions. These inclusions are acceptable as long as they do not take away from the durability or beauty of the stone. Emeralds are often characterized by a garden of included crystals trapped within, known as the "jardin", because under magnification you will see all sorts of lovely patterns resembling foliage in a garden. A flawless, clear emerald is very rare and is usually found in only small sizes. Small to medium sized stones are often faceted in the "step" or emerald cut. The gem is also lovely when cut into a cabochon or dome shape. Sometimes emeralds are even carved.
Although a hard stone, emerald will chip easily, since it tends to be somewhat brittle, so special care should be given in wearing and handling. Since natural Emerald can contain liquid and gas inclusions, jewelers use care as this gemstone needs to be kept away from any high heat. Because of emerald's popularity and value, imitations are abundant. Glass (manufactured complete with "flaws"), doublets or triplets such as "aquamarine emeralds" and "Soude' emeralds," which are clever imitations made by inserting layers of green glass (or, more frequently, a green cementing agent) between pieces of aquamarine or quartz "crystal" are often encountered. Also, fine synthetic emeralds have been produced for many years with nearly the same physical and optical properties (color, hardness, brilliance) as genuine emerald. Careful examination by a qualified Gemologist can usually identify the origin as natural or synthetic. Techniques to enhance color and reduce the visibility of flaws are also frequently used. A common practice is to boil the emerald in oil (sometimes tinted green) with the use of a vacuum to force the oil into the openings. Oiling is an enhancement that goes back to early Greek times. This is a widely accepted trade practice, when colorless oils are used and it is properly disclosed, since it is actually good for the stone in light of its fragile nature. Oiling hides some of the whitish flaws, which are actually microscopic cracks, filling the cracks so they be come less visible. The oil becomes an integral part of the emerald, unless it is subjected to some type of degreasing procedure. The development and use of the ultrasonic cleaner has brought to light the extensiveness of this practice. Never clean emeralds in an ultrasonic cleaner or use a steam cleaner.
All emeralds that are used for jewelry go through the same six-part enhancement process to become the gemstones we know. The steps are sawing, preforming, cutting, polishing, cleaning, and clarity enhancing. Virtually all emeralds require the process of clarity enhancement. This process involves immersing the emerald into a colorless or near-colorless medium. An infinitesimally small amount of the clarity-enhancing medium penetrates open fissures. The volume is so small that it is usually not measurable by weight (typically as little as 1/100,000 of a gram). It should be assumed that every emerald has been processed in this manner unless it has an accompanying laboratory report indicating that there is no evidence of a clarity enhancement medium. Such extraordinarily rare gems command a considerable premium.
Agents used for clarity enhancement are colorless or near colorless: oils (fair stability), prepolymers and uncatalyzed resins (fair to good stability), paraffin (good stability), and polymers (excellent stability). Using any of the above, except for polymers, to enhance an emerald produces good initial results, but there are some limitations to the effectiveness of these enhancements. Over time, the agents will escape the fissures in the emerald and again reveal the inclusions. Cleaning an emerald using traditional jewelry cleaning products and techniques will also serve to remove these agents from the fissures. The emerald will need to be enhanced, occasionally by "oiling", to maintain its beauty.
TREATMENT: Commonly oiled to hide flaws. Uncommonly; colored oil is used.
MOHS HARDNESS: 7.5-8 A hard stone, but subject to care because of internal liquid filled inclusions and fractures.
CHEMICAL COMPOSITION: Be 3 Cr 2 Si 6 O 18
REFRACTIVE INDEX: o=1.577, e=1.583 (+/- .017)
(The angle light is bent traveling through a gemstone)
DENSITY (SPECIFIC GRAVITY): 2.68-2.78
(The number of times heavier a gemstone is compared to water)
PRINCIPAL SOURCES: Colombia, Zambia, Brazil, Afghanistan, and Zimbabwe
