Buying a Gemstone
Gemstones are all about color, and the quality of a gemstone is judged by its hue, its tone, and its saturation. Color is the most important defining factor of a gemstone and the value of any gemstone will be determined in large part by its color. The most highly prized gemstones have one primary “pure” hue such as red (ruby), blue (blue sapphire), and green (emerald). The tone of the gemstone indicates the depth of its color, which can range from black (the deepest) to almost colorless (the shallowest). Gemstones with a tone between “medium light” to “dark” are the most popular. The saturation of a gemstone is the measure of its color intensity, with the specimens of “strong” and “vivid” saturation being the most valuable.
Almost all gemstones have internal inclusions of one type or another. Non-synthetic gemstones with no flaws are extremely rare and valuable. The general degree of internal inclusion found in a gemstone also correlates to its mineralogical family. Gemstones such as tanzanite and aquamarine are generally found to have very few internal imperfections whereas emeralds and rubies are naturally found to have many inclusions. You should also realize that because each gemstone was formed under slightly different circumstances in the earth, they each bear a different set and degree of characteristic inclusions which in many cases are not considered detriments of their original beauty.
As opposed to the system used for diamond classification, there isn’t a universal “ideal” cut optimized for the brilliance of color gemstones. Instead, a good quality cut for gemstones is one that accentuates even color tones, reduces the prominence of inclusions, increases reflection and therefore refraction of incident light (avoidance of “windows”), and showcases the maximum carat weight of the gemstone when set in jewelry.
Gemstones Carat Weight
The carat weight of a gemstone is not necessary a good measure of its size. Because rubies have a higher density than diamonds, a 1 carat ruby will be smaller than a 1 carat diamond. Some 1ct gemstones will have a larger depth than others and therefore a smaller crown diameter.
Nearly every single gemstone on the open market today has been heat-treated. It is a very common practice which has been employed for centuries to bring out the purest of the sapphire's hues. The controlled heating of a gemstone is considered a finishing process to complete what nature has started, and is a widely accepted and expected practice by the jewelry industry, the American Gem Trade Association (AGTA), and all major reputable gemstone retailers. The effects of heating are as permanent as the gemstones themselves because it is merely a continuation of the gemstone's formation process deep in the earth. Fine quality unheated gemstones (which should be accompanied by a certification from an independent third-party laboratory stating that the gemstone exhibits no indication of heating) are exceedingly rare and generally command exorbitant prices.