The Rock of the month for May 2013 is also the birthstone for the month of May! Emerald is the green color of the mineral family Beryl. Aquamarine is also a member of the beryl family. Emerald gets it’s green color from having trace amounts of the mineral chromium and sometimes vanadium in its chemical makeup. Emerald is a fairly hard gemstone with a hardness of 7.5 – 8 on the Mohs scale.
While green is the primary hue for an emerald, it can have traces of yellow or blue. To be classed as an emerald, not only must the primary hue be green, it must be a deep green. A light green beryl is just known as “green beryl”.
Emeralds are rarely clear, they are known as a Type 3 gemstone. This means that inclusions or “stuff” inside of the gemstone is common. These inclusions can impact the stability of the gemstone causing it to be subject to cracking or breaking – so be careful when choosing an emerald!
Most emeralds are treated with an oil, such as cedar oil, after they have been cut. This is a common practice in the gemstone world. There are also less acceptable methods of treating the gemstone so if you are purchasing an emerald for jewelry always ask your jeweler what, if anything, has been done to treat the emerald.
Lab created emeralds are also common in the market. These gemstones are like mother nature would create except that they are grown in a lab under controlled conditions. This limits the amount of inclusions in the stone so the emerald can be very clear. A common name for a lab grown emerald is Chatham (TM).
In ancient times, when there was less knowledge about chemistry and fewer ways to test stones, all green stones were called emeralds. As we have learned more advanced ways to test stones, we can now differentiate the various green colored gemstones and minerals. But emeralds have been found in the jewelry collections of royalty throughout history. The emerald is truly a noble gemstone!