Batu Permata Zamrud
Zamrud dalam bahasa inggrisnya dikenal sebagai Emerald
Zamrud (Be3Al2SiO6) adalah batu permata atau batu mulia yang berwarna hijau sampai hijau tua. Zamrud termasuk mineral silikat beril (mengandung beryllium) dan warna hijaunya disebabkan oleh kelumit kromium. Adanya vanadium dan besi yang menyertai kelumit kromium akan menyebabkan ragam zona pada warna hijau tersebut. Kekerasan zamrud termasuk tinggi (7,5 dalam skala Mohr).
Penghasil zamrud kualitas tinggi adalah Kolombia, Siberia, Afrika Selatan, Zimbabwe, Australia, dan Brasil.
In gemology, 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, red red beryl or bixbite, not to be confused with bixbyite, and colorless goshenite.
Emeralds, like all colored gemstones, are graded using four basic parameters–the four Cs of Connoisseurship: Color, Cut, Clarity and Carat weight. Before the 20th century, jewelers used the term water, as in “a gem of the finest water”, to express the combination of two qualities: color and clarity. Normally, in the grading of colored gemstones, color is by far the most important criterion. However, in the grading of emeralds, crystal is considered a close second. Both are necessary conditions. 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 gem.
In the 1960s, the American jewelry industry changed the definition of “emerald” to include the green vanadium-bearing beryl as emerald. As a result, vanadium emeralds purchased as emeralds in the United States are not recognized as such in the UK and Europe. In America, the distinction between traditional emeralds and the new vanadium kind is often reflected in the use of terms such as “Colombian Emerald”
The word “Emerald” is derived (via Old French: Esmeraude and Middle English: Emeraude), from Vulgar Latin: Esmaralda/Esmaraldus, a variant of Latin Smaragdus, which originated in Greek: σμάραγδος (smaragdos; “green gem”)
Most emeralds are oiled as part of the post-lapidary process, in order to fill in surface reaching cracks, improving their clarity and stability. Cedar oil, having a similar refractive index, is often used in this generally accepted practice. Other liquids, including synthetic oils and polymers with refractive indexes close to that of emerald such as Opticon, are also used. The U.S. Federal Trade Commission requires the disclosure of this treatment when an oil treated emerald is sold. The use of oil is traditional and largely accepted by the gem trade, although oil treated emeralds are worth multitudes less than un-treated emeralds of similar quality. Other treatments, for example the use of green-tinted oil, are not acceptable in the trade. Gems are graded on a four step scale; none, minor, moderate and highly enhanced. Note that these categories reflect levels of enhancement, not clarity. A gem graded none on the enhancement scale may still exhibit visible inclusions. Laboratories tend to apply these criteria differently. Some gem labs consider the mere presence of oil or polymers to constitute enhancement. Others may ignore traces of oil if the presence of the material does not materially improve the look of the gemstone.
Given that the vast majority of all emeralds are treated as described above, and the fact that two stones that appear visually similar may actually be quite far apart in treatment level and therefore in value, a consumer considering a purchase of an expensive emerald is well advised to insist upon a treatment report from a reputable gemological laboratory. All other factors being equal, a high quality emerald with moderate enhancement should cost severely less than an identical stone graded none
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. The inclusions and fissures within an emerald are sometime described as ‘the garden’, because of their mossy appearance. These imperfections within the stone are unique to each emerald and can be used to identify a particular stone. 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. Faceted Emeralds are most commonly given the Oval cut, or the signature Emerald cut, a rectangular cut with facets around the top edge.