Emerald

Emerald

May’s birthstone

Colours

Green

Family

Beryl: Be3Al2Si6O18

Hardness

7.5 – 8

Refractive Index

1.56 – 1.60

Specific Gravity

2.68 – 2.74

Crystal System

Hexagonal

Enhancements May be enhanced
Major Sources

Brazil, Columbia, Afghanistan, Zambia, Zimbabwe, Russia

Warnings for Care Very susceptible to damage by even low heat

Emerald Facts

Emerald is the most precious member of the Beryl group. The name Emerald is derived from the Greek "smaragdos", which in turn came from the Persian, then via the Old French "esmeralde" to its modern form, and literally  means 'green gemstone.' Its green to many is incomparable, and is therefore call "emerald green", a phrase in common use both inside and outside the mineralogy world. 

 

Emerald is classified as one of the traditional four precious gemstones along with Ruby, Sapphire, and Diamond, is the birthstone for May and in many cultures is used to commemorating the 20th and 35th wedding anniversaries.

Topics Of Interest:
Emerald - What causes the colour
Purchasing Emerald
Mineable Deposits
Emerald - Common Treatments
Important & Famous Emerald
Emerald - The Legend

Emerald - What Causes the Colour

The causal element in Emerald's that produces its distinctive  green color is trace amounts of chromium and sometimes vanadium.

Only the finest of Emeralds are transparent, with almost all natural emeralds containing some characteristic inclusions, know as a "Jardin" (garden). These inclusions can be liquid or gas bubbles, healing cracks and foreign crystals captured in the emeralds lattice. It should be noted that these are not necessarily classified as faults, but are evidence of the genuineness of the stone.  For that reason Emeralds are generally more fragile than other Beryl’s and must be handled with more care. With Emerald, even more than other colored gems, it is the color of the stone which is the chief determinant of value, followed by clarity, carat weight and cut.

 

Color
While the colour of Emeralds is extremely variable (the phrase "100 different Emeralds, 100 different colours, holds  significant truth), they are, by definition Emerald Green. That is to say  a medium or darker green to blue green Beryl, in which the green color is derived from trace quantities of chromium, vanadium, or a combination of both. The most popular and valuable color is a slightly bluish green in a medium dark tone with strong to vivid saturation, epitomised by the Zimbabwean deposit of  Sandawana. The term "Colombian" Emerald is often used to describe vivid, slightly bluish / yellowish green stones of medium, to medium dark color, no matter what their actual geographic origin. Emeralds of lighter color are sometimes called "Brazillian or South American" Emerald, even if they were mined in Africa.

 

Lighting
Emerald is another classic daylight stone. Artificial light while making the green colour appear richer will expose inclusions and fractures, and thereby reduce a stones natural beauty

 

Clarity
Clarity while important in all gemstones is of secondary concern behind colour in Emeralds. Unlike other members of the Beryl family, Emeralds commonly contain inclusions and other flaws. These flaws are not looked on as negative aspects, like they would be for other gemstones. Indeed, these flaws are considered part of the character of the stone and are used to assure the purchaser of a natural stone. In fact the determinative identification in a top quality eye clean Sandawana Emerald is the presence of minute Rutile needles. Without these many collectors and jewellers, will not accept the stone as being from this source locality.

 

Cut
The subtle beauty of this unique gem, lends itself to the simplest of cuts. A rectangular or square cut with  oblique corners forming an octagonal shape, with simple step  facets has been the preferred cut of choice for Emeralds for hundreds of years. This cut know today as simply the emerald cut is one of the oldest in existance.  The emerald cut has two distinctive benefits which enhance the beauty and longevity of the stone. The simple step facets allow the natural colour of the stone to dominate; the absence of multiple additional facets reduces the brilliance of the cut and enhances the saturation and hue of the stones. The clean design of this cut greatly reduces mechanical strain than can be applied to the stone during the cutting process, this to a certain extent ensures that inclusions which are often inherent lines of weakness in the stone do not manifest themselves as fractures, when the stone is set 

 

Emeralds are however also cut in many other of the mainly classical (simpler) shapes, if the rough material is deemed to be of gem grade. Less transparent material  containing a large number of inclusions, is often cut into a gently rounded en-cabochon cut (cabochon), or even into beads.

Emeralds are formed by the crystallization of rising magma and metamorphism, deposits are therefore mainly found in or proximal to pegmatitic veins. Mining of Emerald  is almost exclusively from the host rock, where the crystals have grown in either small veins or on the walls of cavities.

 

Colombia is one of the worlds major  centers of mining Emerald, with excavations going back to the time of the Incas. The Muzo mine, northwest of Bogota, produces fine-quality stones of a deep green color, from the softer black carbonaceous limestone host rock. This mine is believed to have produced many of the most prized Inca Emeralds.

 

The Chivor mine, northeast of Bogotá and a secondary deposit nearby (Gachala) are other important Colombian deposits still in production today, and yielding significant gem quality stock from a limestone and shale host rock.

 

Brazil has various lower grade deposits at Bahia, Goias and Minas Gerais. These are of minor economic importance, with the  stones being lighter than the Colombian ones, and mostly yellow-green. They are however often free from any inclusions.

 

In the late 1950's Emeralds were discovered in southern Zimbabwe (Rhodesia), the most significant deposits to date are  the Sandawana and Belingwa mines, which produce small high quality Emeralds with a most intense blue green colour from a black hornblende shale.

 

Numerous other deposit are found worldwide in such localities as South Africa, Zambia, Afghanistan, Ghana, India, Pakistan, Australia, North Africa and Northern Europe, to name a few. In all cases these deposits are characterised by pegmatitic volcanism.

The oiling of Emeralds has become common practice as the last stage in the polishing process, being most effective in those stones that have inclusions or fractures that reach the surface. This oiling process refers to the practice of immersing emeralds in a colorless high viscosity oil or resin. Often this is done using a partial vacuum  to assist penetration. Non-standard treatments go beyond this to using green colored oils and hardened, epoxy-like resins (Opticon).

 

These treatments dramatically improve the appearance of the gems in the short term, but necessitate special care in cleaning and setting, and a reapplication of the process to ensure its longevity. Steam cleaners, solvents and ultrasonic baths can remove the oils, making inclusions that had barely been visible stand out in sharp relief. This "damage" is only temporary, since emeralds can be re-oiled , either in or out of their settings.

There are many well know, large Emeralds in existence. In the Viennese treasury there is a jug 12cm high and weighing 2205ct, cut from a single Emerald crystal. Another of the worlds largest carved and engraved Emeralds is the so-called 'Mogul Emerald'. It dates from around 1695 and weighs 217.80 carats. This legendary Emerald was auctioned by Christie's of London for 2.2 million dollars to an unidentified buyer, on September 28th 2001.

 

Emeralds have been held in high esteem since ancient times, and for that reason are almost common place in the crown jewels on many nations.

 

In Istanbul's Tokapi Palace there are exhibits with items of jewelry, writing-implements, each lavishly adorned with emeralds and other gems. In the case of the Emerald Dagger the entire handle is carved from a single piece of emerald.

In the Iranian National Treasury, the diadem of the former Empress Farah is  adorned with multiple large Emeralds

Her majesty, Queen Elizabeth II, has in her collection  the "Cambridge and Delhi Dunbar Parure", a fantastic suite of Emerald jewelry which includes an Emerald diadem.

Over time many cultures and civilizations have held Emerald to be an important gemstone The Incas and Aztecs of South America, regarded the Emerald as a holy gemstone. The  Egyptian pharaohs believed that Emerald would ensure eternal youth in the afterlife; hence many mummies were adorned with the stone. The Vedas, the holy scriptures of the Indians, makes mention of  the precious green gem and its  healing properties: 'Emeralds promise good luck...' and 'The emerald enhances the well-being...'.

 

Emerald is the birthstone for those who are born in May, and in many cultures  is the gemstone for commemorating the 20th and 35th wedding anniversaries.

Precious Semi-Precious Gemstones

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