I am sure we all know the 4 C's of Diamonds: Color, Clarity, Cut, and Carat Weight. These four characteristics are judged somewhat evenly when selecting a diamond. Clarity usually refers to very small inclusions visible with magnification.
We think a bit differently when evaluating colored gems. The first priority is Color. Is the color pleasing and saturated? Almost without exception lighter shades are priced less than deeper hues. Think about the pastel shades of Amethyst, Aquamarine, Peridot, and even Opals. They can be very beautiful but should cost less than the richly colored ones. Beware of muddy colors.
Clarity is an issue in some colored gems. We can expect inexpensive color like some Garnet, Amethyst, Aquamarine to be clean -- free of visible inclusions. But there are many gems that are just not found without inclusions: Emerald, Paraiba Tourmaline, Rubellite, Ruby, Sapphire, and others. So with these gems the least inclusions the better.
Cut can be improved sometimes and Carat Weight is what it is.
The Fifth C is Certification. This becomes very important when purchasing rare and unusual gems such as Paraiba Tourmaline. To be classified Paraiba the tourmaline must contain copper. It can be from Brazil or Africa. Beware of the many blue and green tourmalines that do not contain any copper being sold as Paraiba. Do not purchase a significant gem without a certificate from a respected lab stating the gem contains copper.
