Mohs hardness 7.5-8, Specific gravity 2.68-2.78, Refractive index 1.560–1.602. Emeralds are a green member of the Beryl clan, colored green by trace amounts of chromium and sometimes vanadium. Most emeralds are highly included, so their toughness and resistance to breakage is classified as generally poor. The word Emerald is derived from Old French: Esmeraude and Middle English: Emeraude, and from Latin: Esmaralda/Esmaraldus, a variant of Latin Smaragdus, which originated in Greek: (smaragdos; "green gem"); its original source being either the Hebrew word izmargad meaning "emerald" or "green" or the Sanskrit word marakata meaning "green." The name could also be related to the Semitic word baraq ("lightning" or "shine") (cf. Hebrew: bareqeth and Arabic: barq "lightning"). It is the same source for the names Persian (zomorrod), Turkish (zümrüt), Sanskrit (maragdam), Russian (izumrud) and Armenian zmruxt. Emeralds, like all colored gemstones, are graded using four basic parameters, the four Cs of Connoisseurship; Color, Cut, Clarity and Crystal. The last C, crystal is simply used as a synonym that begins with C for transparency or what gemologists call diaphaneity. 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 crystal. Normally, in the grading of colored gemstones, color is by far the most important criteria. However, in the grading of emerald, crystal is considered a close second. Both are necessary conditions. A fine emerald must possess not only a pure verdant green hue, but also a high degree of transparency to be considered a top gem.
Color is divided into three components: hue, saturation and tone. Yellow and blue, the hues found adjacent to green on the spectral color wheel, are the normal secondary hues found in emerald. Emeralds occur in hues ranging from yellow-green to blue-green. The primary hue must, of course, be green. Only gems that are medium to dark in tone are considered emerald. Light-toned gems are known by the species name, green beryl. In addition, the hue must be bright and vivid.
Clarity. Emerald tends to have numerous inclusions and surface breaking fissures. Unlike diamond, where the loupe standard, i.e. 10X magnification, is used to grade clarity, emerald is graded by eye. Thus, if an emerald has no visible inclusions to the eye it is considered flawless. Stones that lack surface breaking fissures are extremely rare and therefore almost all emeralds are treated, "oiled", to enhance the apparent clarity. Eye-clean stones of a vivid primary green hue 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.
Treatments. Most emeralds are oiled as part of the post lapidary process, in order to improve their clarity. 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 use of oil is traditional and largely accepted by the gem trade. Other treatments, for example the use of green-tinted oil, are not acceptable in the trade. Given that the vast majority of all emeralds are treated as described above, and the fact that two stones that appear to be similar in quality may actually be quite far apart in treatment level. All other factors being equal, a high quality emerald with an enhancement level graded moderate should cost 40–50% less than an identical stone graded none.
EMERALD - to promote love, romance, joy, cleansing, clairvoyance, clear vision, memory, faith, intuition, serenity, intelligence and communication. This is a truth-promoting stone, inspiring deep knowing from within. Emerald - “Stone of Successful Love” domestic bliss, stimulates heart charka, harmony, fidelity, joy, all healing.
The Breastplate of Aaron: a ceremonial religious garment set with twelve gemstones that represented the twelve tribes of Israel. It was square -- a span [22 centimeters] long and a span wide -- and folded double. Then they mounted four rows of precious stones on it. In the first row there was a ruby, a topaz and a beryl; in the second row a turquoise, a sapphire and an emerald.
The Twelve Tribes of Israel In Exodus 28:17-21, specific gemstones were associated with the twelve tribes of Israel. People of Jewish heritage may wish to select their birthstones based on tribal names. Historians have complied several lists of which stone goes with each name. Emerald is associated with the tribe of Levi.
Christianity influenced the symbolism of gemstones. Specific gemstones were also associated with the twelve apostles. Emerald associated with apostle James/John.
May modern birthstone- emerald, ancient traditional birthstones: Arabic - emerald, Hindu - emerald, Polish - emerald.
June ancient traditional birthstones: Hebrew - emerald, Roman - emerald.
Zodiac gemstone for Cancer - emerald
Guardian angel Muriel and his talisman stone - emerald.
Emerald care: Wash with warm soapy water, Avoid harsh detergents, Never clean ultrasonically, Never steam clean.