The Different Beryl Varieties
The article page is an excerpt from the book Gem Dealer’s Secret,written by Sondra Francis, and discusses the different varieties of Beryls.
Aquamarine, Emerald, Morganite
Golden Beryl, Red Beryl, Green Beryl and Goshenite
|Colors:||Blue, green, red, pink to orange, yellow, and colorless|
|R.I.:||l.56 – l.59|
|Durability:||Slightly fragile to tough|
|S.G.:||2.67 – 2.84|
|Treatment:||Heating: aquamarine and morganite. Oiling and synthetic resins: emerald|
|Hardness:||7 1/2 – 8|
|Availability:||Steady supply of aquamarine and emerald in a variety of sizes, other varieties can be more difficult to find|
|Localities:||Emerald: Colombia, Brazil and Zambia. Aquamarine: Brazil, Nigeria and Madagascar|
|Price:||low to very expensive|
|Common shapes:||Emerald cuts, ovals and cushions|
Aquamarine was the talisman of the sailor for centuries, its colors resemble those of the sea and it has a delicate watery appearance that perfectly suits its name. It is the blue-green to green-blue variety of beryl. It ranges from an icy pale blue to a medium dark blue color. Although, even in the darkest shades, its color is always a pastel blue with varying amounts of green as a secondary color. Aquamarine can be found in fairly large sizes. Light colors can be low in price but more saturated blues can be moderate to expensive.
Aquamarine is readily available in eye-clean stones. Because the color is light, any inclusions in the stone would be easier to see. Its hardness is about 8: it is a fairly tough gemstone. You can assume that an aquamarine has been gently heated. The aquamarine rough is usually a bluish- green when mined; heating drives out the green overtones and intensifies the blue color. The color generally darkens as the size increases: finding a small stone with a medium to dark blue color may be challenging; but larger stones can be found in the darker colors.
Aquamarine is most often cut into emerald cuts. Cushions, and ovals are also readily available. If you are buying an aquamarine, the color will be your most important consideration. Examine the stone to be sure that it does not have excessive depth in the pavilion to make the stone appear darker. This will make it heavier and more difficult to set. In some very dark blue Brazilian aqua there may be some inclusions, but eye clean stones in lighter shades are generally easy to find.
Emerald, the “green fire” of gemstones, enflamed the greed of the Spanish Conquistadors arriving in South America into murderous campaign to discover the source. Pissarro, the leader of the Spanish, ordered that Incan rulers were to be tortured until they revealed the location of the emerald mine. In l557 the Spanish finally found the fabulous Muzo mine in what is now Colombia. Even today mining in Colombia is still a very dangerous business.
Emeralds are the emerald green variety of beryl; chromium is the trace element that usually creates this color. Although most African emeralds are colored by the presence of vanadium. The finest emeralds are an intense pure medium green, without blue or yellow modifying tones. The purity of the green is critical to the value of an emerald. If the emerald is too dark or too light in color, the per carat price will drop considerably. Overtones that are blackish or mossy devalue the stone.
Small fine emeralds will not have eye-visible inclusions, but as sizes increase inclusions are generally more apparent. Top quality emeralds are exceptionally rare in sizes over a carat and are very expensive. Most emeralds have some eye visible flaws that are kindly referred to as “jardin” or “garden.”
As long as the stone has very fine color and is transparent and cut to exhibit the “green fire”, the emerald will command a high price per carat even with a few visible inclusions. Some inclusions can be clues to the emerald’s origin.
To judge the clarity of an emerald, see if you can see the back facets when looking through the table. If the back facets are not visible, it is very heavily included and does not fall in the high quality category. Transparency is the second critical factor in judging an emerald’s quality. The less transparent the stone, the lower the price per carat.
Top quality emeralds from Colombia origin will command the highest possible prices because of their intense vivid green color. The country of origin alone tells you nothing: other emerald sources produce very fine stones, and Colombia produces a lot of low quality material. Only a tiny percentage of any mine’s gemstone production falls into the high quality category.
Brazil produces huge quantities of emeralds. Brazilian emeralds range from a light green to a pleasant medium dark green color. Zambia also produces fine emeralds; generally they tend to have a bluer hue than Colombian or Brazilian emeralds. Very fine emeralds are mined in small quantities in Pakistan and in Zimbabwe. The emeralds from Zimbabwe are often called “Sandawana” emeralds which refers to the area in which they are mined.
If you are in the market for an emerald, remember that “brightness” of color is an important consideration. Good cutting and fewer inclusions contributes to an emerald’s brightness. Brighter stones sell for more per carat than duller stones with a darker color.
The majority of emeralds are cut into the appropriately named emerald cut, the rectangular step cut. This cut accentuates the emerald’s green color. Pear shapes, ovals, rounds, and heart shapes can also be found but are less common. Judge an emerald’s beauty factor by looking at the stone face up. Emeralds may not always be cut with symmetrical pavilions, but if the stone has good brilliance and transparency this is not too important. It is not unusual to find gemstones cut from expensive rough to be slightly asymmetrical in the pavilion. Check the depth of the pavilion, sometimes they will be quite deep and may be hard to put into a mounting.
Cabochon cut emeralds, if they have a pure deep color and are not too included, can be very beautiful and fall into the expensive price range.
Assume that an emerald has been oiled or treated with a synthetic resin unless you are looking at an exceptionally high quality stone. Occasionally emeralds will have color zones you can notice if you carefully examine the stone. If the emerald has been carefully cut the stone will face up with no noticeable detraction from its beauty. In this case, there will be no price difference.
Emerald has a relatively high hardness of 7 1/2 to 8; but because of the inclusions it should usually be treated as a fragile stone and set into o a protective mounting. If an emerald is put into an ultrasonic or steam cleaner, the oil could be cleaned out of the fractures, suddenly making them much more visible. Of course, a very fine stone will not have oil because it doesn’t have fractures. Still, it is advisable to avoid ultrasonic cleaning of an emerald. The best way to care for an emerald ring would be to remove it when washing one’s hands and applying lotions. Emeralds do not deserve to be plunged into dishwater. If an emerald is dirty, remove particles lodged behind the stone with a wooden tooth pick and soak the ring in a gentle ammonia solution. A cotton swab can be used for a final mop-up. Professional cleaning is recommended for very dirty stones.
Other Varieties of Beryl
Morganite is the pink to orangey-pink variety of beryl. It was named after American financier J. P. Morgan, who was an avid collector of unusual gemstones. It is not common: most stone are pale and fall into the low price per carat category. Darker fine pinks are rare and will be moderate in price if you can find one. Small stones are unusual to find because they generally have too pale of a color. Most morganite is heated which eliminates the orange color and intensifies the pink.
Golden beryl, also called heliodor, is the yellow to gold variety of beryl. Golden beryl may not be easy to find, but they will fall into the low price per carat category unless exceptional in color and large in size.
Green Beryl is pale green material that does not fall into the emerald classification. It is low in price per carat, because there is not a great demand for green beryl on the present market.
Red Beryl or bixbite is the varietal name for the very rare red beryl. It is only mined in one place: the Wah Wah Mountains of Utah. Red beryl is extremely rare. Only small stones, mostly under one-half carat size, are available and these are generally visibly included. They are an intense red color and resemble very fine ruby. Like emerald and ruby, red beryl has chromium as a trace element, but manganese gives it the red color; it has been marketed as “American red emerald.” Prices fall into the expensive category.
Goshenite is the colorless variety of beryl. It has little use as a jewelry stone but may be of interest to collectors. Prices will be in the low range.
Occasionally beryl varieties will display chatoyancy and can be cut to show a cat’s-eye. Aquamarine, green beryl and golden beryl cat’s-eyes can be found, emerald cat’s-eyes are also seen but they are very rare. Cat’s-eye beryls, like other phenomenal stones, will be cut into oval or round cabochons. The eye portion on most cat’s-eye beryls are not usually as well defined as the eye displayed by other varieties. To bring out the cat’s-eye, the stone can be mounted on a polished metal surface to help reflect a stronger “eye.” The beryl cat’s-eyes, except for emerald, will fall into the low to moderate per carat prices depending on size, color, sharpness of eye, and transparency. Emerald cat’s-eyes would fall into the expensive category, if you could find one.
Another gemstone rarity is trapiche emerald; this is a very unusual combination of a feldspar mineral, albite, that forms intergrown with emerald. It forms in a well-defined hexagonal shape with the albite outlining triangular sections of brilliant green emerald. It is like a star that is a permanent part of the structure of the gemstone instead of an optical effect. They are not large. If you want a trapiche emerald, you probably will need some time to chase one down. Prices will fall in the medium to expensive range.