The mineral beryl—beryllium aluminum silicate—can be pink, red, green, yellow, blue, brown, or black. The majority of our gem-quality beryls come from pegmatites, which yield large crystals that are relatively free of inclusions. This makes beryls ideal for jewelry, but with the exception of emerald and aquamarine, the lesser-known beryl varieties are mainly collectors’ stones.
Emeralds are the the most popular variety of beryl, but they can be expensive. Sea-green aquamarine is considerably more affordable. Its name comes from the Latin aqua (water) and marina (of the sea). It owes its color to traces of iron. Top-quality aquamarine is moderately strong, medium-dark blue to slightly greenish blue. There are no agreed upon criteria for distinguishing lighter-colored emeralds from aquamarine in the gem trade. However, aquamarine typically exhibits a lighter tone and saturation than emerald.
Many aquamarines are eye-clean. Because of the relative clarity of the crystals—notably their lack of fluid-filled inclusions—aquamarine can be safely heat-treated to a deeper blue color. In the United States, aquamarine competes with blue topaz in the marketplace, but it is very popular in Europe and Japan.
Due to their light tone and saturation, large aquamarines tend to have the best color. Fortunately, supply is not a problem. Ten-carat stones are common, and faceted stones of 1,000 carats are also known. Crystals up to 100 pounds are also employed as a medium for small sculptures and carvings.
There is no agreed-upon criteria for distinguishing emerald and green beryl in the gem trade. Green beryl can vary from very strongly bluish green to yellowish green in hue. It is generally distinguished from emerald by its lighter tone and saturation. This is caused by the relative abundances of the same trace elements that color emerald: chromium, vanadium, and iron. In general, green beryl will have more iron and less chromium or vanadium than emerald. The presence of chromium also prevents the color from drifting towards shades that resemble aquamarine.
Beryl that is pink, rose, salmon, or peach is called morganite in the trade. These stones typically have low to moderate tones and saturations. The gem was discovered in Madagascar in the early 20th century and stones from that island remain the standard for quality. The variety was named for J. P. Morgan, the American financier and gem collector.
The color of morganite is determined by traces of manganese. Pink and rose hues, which are the most marketable, can be obtained by gently heating salmon and peach material to eliminate unwanted yellow and orange secondary colors. A wide range of sizes is readily available in the market, but due to their light tones and low saturations, larger stones typically have the best color.
In 1917 medium to dark blue beryls were found in Brazil. The gem industry went wild over the new stone until its color was found to fade over time. Experts later determined that the color of the new maxixe beryls was due to color centers caused by natural radiation. Color centers are minute defects in the internal structure of a crystal. These internal defects are unstable and can be altered by the application of either light or heat, which causes their color effects to disappear. The bleaching or fading of maxixe beryl occurs at an unpredictable rate. Irradiation will restore the blue color, but it will not be permanent.
Yellow or golden beryl is often called heliodore, from the Greek helios (sun) and doron (gift). The color, which is caused by traces of iron, ranges from greenish yellow to orangey yellow with light to medium tones and saturations. Larger stones display the best color.
Although it is less common than aquamarine, heliodor does not command the same price. Eye-clean stones may be heated to produce more marketable aquamarine color or irradiated to improve the golden or yellow hues. Occasionally colorless beryl is also irradiated to produce a yellow beryl.
Red beryl is a rare variety of beryl with darker tones and more saturated colors than its cousin morganite. This raspberry red stone is occasionally called red emerald or bixbite—after Maynard Bixby, the man who discovered it in 1897. Neither of these names has gained currency in the trade.
Like morganite, the color of red beryl is determined by trace amounts of manganese. However, in red beryl, larger quantities of this color-causing agent produce a highly saturated pure red—although cut gemstones can vary from purplish red to orangy red due to pleochroism.
Like emerald, red beryls can be heavily included. Their clarity is affected primarily by fractures, but they are also known to have two-phase inclusions, solid crystals, fingerprints, and color zoning. For this reason, red beryls are typically treated with colorless oils or resins to improve their apparent clarity.
Red beryl is the rarest of the beryls and it is expensive even though it is known mainly among collectors. It has been found in only a couple of locations where both the yields and the average size of the stones are small.
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