CHEMISTRY Be3Al2Si6O18 + Fe
REFRACTIVE INDEX 1.567 – 1.590
HARDNESS 7.5 – 8
SPECIFIC GRAVITY 2.66 – 2.80
HEAT SENSITIVE No
SPECIAL CARE INSTRUCTIONS None
ENHANCEMENTS May be heat treated to remove green tint. Very common, undetectable.
*Wearability is graded as Excellent, Very Good, Good, Poor, and Forget It! For more details see the article on “Hardness and Wearability.”
Aquamarine is a member of the beryl family, as is emerald. Aqua is known for its blue or blue green coloring, which accounts for its name. The legends behind aquamarine all have to do with the sea and water.
Aquamarine is the birth stone for March. It is a popular gem that wears well, is readily available and moderately priced.
One of the most remarkable qualities of this gem are the sizes it is available in. Gems have been cut that weigh several hundred carats, way too large to be worn. Due to this, the price of aquamarine doesn’t vary in sizes above one carat. A 50 carat aquamarine will be worth the same price per carat as a one carat gem of equal quality. The price is dependent on its clarity, the depth of color and to a lesser extent the purity of color.
Another interesting feature of this gem are its inclusions. Beryls, and aquamarine in particular, are known for having long, hollow tubes. This is a distinctive feature and will identify a gem as a member of the beryl family.
If there are enough of these hollow tubes, cats eyes or stars can be produced with proper cutting. A cats eye aquamarine is a thing of beauty and is highly prized by collectors. Prices will be very close to that of a clean, faceted gem with the same coloring. Star aquamarine is even more rare than a cats eye and can demand a premium price.
This beautiful gem receives its coloring from trace amount of iron. The color can be very light to moderately dark. You will rarely see an aqua that is darker than a Swiss blue topaz and when you do the color is usually enhanced by the way they are cut.
There is a very dark blue aqua that came on the market about three decades ago, called the Maxixe aquamarine. (That is pronounced ma-she’-she.) This is an irradiated product and the color isnt stable. These have mostly disappeared from the market, but if you are ever offered a very deep blue aquamarine, be cautious. You can distinguish the Maxixe from a natural aquamarine by its pleochroism and its spectrum. In natural aquamarine there is distinct blue and colorless dichroism. The Maxixe aqua has no pleochroism and is blue in every direction. With a spectroscope you will see a narrow line at 6950, a strong line at 6540 and weak lines at 6280, 6150, 5500 and 5810. This is considerably different than natural aquas spectrum with a broad band at 4270 and a diffuse band at 4560.
Most aquamarines come out of the ground with a greenish tint. This will disappear, leaving a pure blue color by heating to 375 degrees Centigrade. Heating aqua to remove its green tinting is very common and used to be done as a matter of routine. Now we have a more sophisticated public and many of them are starting to appreciate the slightly green gems, knowing that they havent been heat treated. This process is impossible to distinguish, so pure blue aquamarines are described as probably heat treated.
When cutting aquamarine, depth of color is usually the primary factor to be considered. Deep designs, like barions and emerald cuts are usually preferred. Faceters should use 43 degree pavilion mains on aquamarine for the highest brilliance. Low crown angles will produce higher brilliance, but higher crowns are often used to deepen the color.
Beryls are some of the easiest gems to polish, with diamond being the most common method. It is probably the high quality of polish that give light aquas such great brilliance they are confused with higher RI gems. While they just have moderate dispersion of .014, light stones with high crown angles will show their spectral colors well. This makes for an outstanding gemstone. While the highest values go to the richer colors, a well cut, light aquamarine is one of the most spectacular examples of the gem world.