Formula Be3Al2(SiO3)6
Color Green
Luster Glassy
Hardness 7.5
Transparency Semi-Transparent
Streak White
Cleavage Poor Basal Cleavage
Fracture Conchoidal
Locality Colombia, United States, Europe

Emeralds are green! If the color is too light the gemstone you are looking at is not an emerald but rather green beryl. Unfortunately there is no standard by which the major gem labs grade between emerald and green beryl. Also, there is no law saying you must distinguish between the two so some people sell green beryl as “emerald”. If the emerald you are looking at looks like Coke bottle glass or lighter I would call it green beryl.

Emeralds are never heat-treated. Most aquamarine is heated to get rid of the natural seafoam green component to produce the blue colored aquamarine we are familiar with. Many other gemstones are routinely heat treated including ruby, sapphire. and tanzanite.

Emeralds are not brittle. Poor quality gemstones including poor quality emeralds can be brittle because they have too many inclusions or cracks running through the gemstone. These low quality gemstones should not be purchased. As a general rule emeralds under $200/carat should be avoided. Moderate to high quality emeralds are suitable for all jewelry types including rings but like any fine jewelry you should avoid situations that would cause damage. All gemstones including diamonds can crack if you hit them just right on granite countertops or other hard surfaces.

Emeralds are harder than quartz, tourmaline, and tanzanite but not as hard as rubies, sapphires, or diamonds.

Emerald enhancements do not “glue” or hold an emerald together. Oil, resin, and polymer clarity enhancements are used to minimize the appearance of inclusions. It is possible to find composite emeralds in the market that are glued together but they are so easy to spot you have no business buying them. Enhancements do not alter the color of the emerald unless green colored oil is used. Using colored oil is not accepted in the US or in Colombia and I have yet to see any colored oils being used in Colombia. Enhancements can easily be removed with chemicals or ultrasonic cleaning and reapplied if needed. The reason emeralds should only be cleaned with warm mild soapy water is so that you don’t remove the treatment. Many other gemstones should not be cleaned in an ultrasonic cleaner either.

Untreated emeralds are only more valuable if they look the same as a comparable treated emerald. Simply removing the clarity enhancement from an emerald does not make it more valuable. Most emeralds look better when they have been clarity enhanced and that’s why it is done. An untreated ugly low quality emerald is not rare or valuable.

Emeralds do not “dry out” or need to be re-oiled every few years. Some emerald treatments are more permanent (polymers) than others but emeralds don’t require frequent oiling. Treatments of emeralds are not done to stabilize the material like you need to do with turquoise or opal. If re-oiling is needed it is easy and inexpensive. Polymers should not require re-oiling since they are a resin with an added hardener. Emeralds should not be subjected to extreme temperatures though as this can affect the enhancement's stability and longevity.

“Oiled” has become the generic term used by many dealers in the US and Colombia for all clarity enhancements. Without a lab report it is impossible to tell what type of treatment was used. Beyond the type of treatment there are hundreds of different formulas used. Branding of treatments has become popular as well with each manufacturer claiming their treatment is superior. My opinion is that the type of treatment has little effect on value and the more important factor is the amount of treatment. Choose emeralds with the least degree of enhancement that you can afford remembering that a moderate degree of enhancement is the norm.  

Nothing looks like a good quality natural Colombian emerald. There is no cheaper alternative in my opinion. Lab grown emeralds are not that cheap and they do not look right. You can almost always see the hydrothermal growth lines and they look too perfect. They lack the warmth that natural emeralds have. No other natural gemstone looks anything like an emerald. If a moderate to high quality emerald is out of your price range there are other beautiful green gemstones such as green tourmaline, chrome tourmaline, tsavorite garnet and peridot. Choose the gemstone that fits your budget and buy the highest quality stone you can afford. I always advise people to choose a smaller size with higher quality over a larger lower quality gemstone. High quality gemstones tend to retain value better during market fluctuations and are just nicer to live with.