Why would two pink tourmalines of identical color, size, and cut vary in price from as little as $5 per carat to as much as $100 per carat? If they are fairly priced, the answer is; they vary greatly in clarity. Stones full of inclusions are lower in clarity, less pleasing to the eye, and less suitable for use in jewelry.
So how do gemstone dealers evaluate the clarity of a cut gem? Most use some variation of the clarity grading system developed by the Gemological Institute of America. This system is a sophisticated scheme somewhat similar to that used by the GIA to grade diamonds. The clarity grades include:
• VVS: Very, Very Slightly Included
• VS: Very Slightly Included
• SI1, SI2: Slightly Included 1 and 2
• I1, I2, I3: Imperfect 1, 2 and 3
• Dcl: Declasse
A complication in grading colored stones arises from the fact that the absolute definition of the above grades varies with the type of gem material. The GIA breaks down colored gemstones into three classes depending upon the likelihood of a particular gem material being included. For example:
• Type I colored stones include aquamarine, morganite, smoky quartz, topaz (blue, yellow, orange, pink, red), zircon (blue), and tanzanite. In the marketplace these gemstones are often virtually inclusion-free.
• Type II colored stones include corundum (all colors), garnets (all species), iolite, peridot, quartz (amethyst, citrine, ametrine), spinel (all colors), tourmaline (blue, orange, yellow, parti-), and zircon (green, orange, red, yellow). In the marketplace these gemstones are usually included.
• Type III colored stones include emerald, and tourmaline (red, pink, watermelon). In the marketplace these gemstones are almost always included.
By the above criteria, a VVS grade aquamarine (A Type I gem, often virtually inclusion-free) would contain only minute inclusions that would be difficult to see under 10X magnification and would be invisible to the unaided eye. A VVS grade rubellite tourmaline would be characterized by noticeable inclusions, easily seen under 10X magnification but barely visible to the unaided eye. Two different types of gemstones would each be classed VVS, but display visibly different degrees of inclusion! Depending upon the type of gemstone, other classes show a similar variation in definition of clarity grade. Considerable training is required to accurately grade the color and clarity of gemstones. I provide the above information only as a general outline of the procedure involved in clarity grading. For further information consult my list of links, and remember; you generally "get what you pay for."
Clarity Grading of Colored Stones