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Gems are usually graded by a type (1, 2, or 3) and by clarity (VVS, VS, SI, SI2, or I). Here's the common grading criteria as used by the GIA (Gemological Institute of America) for colored gems: Type 1 These gemstones are usually free of inclusions. The group includes gems in the quartz family - amethyst, citrine, topaz, zircon, berlys, like aquamarine. Clarity in the type 2 group of gemstones are classified as VVS (minor), VS (noticeable), SI1 (obvious), SI2 (prominent), or I1 (prominent and affecting appearance). Type 2 These gemstones include garnet, iolite, alexandrite, ruby, sapphire, or peridot. Clarity in the type 2 group of gemstones are classified as VVS (minor), VS (noticeable), SI1 (obvious), SI2 (prominent), or I1 (prominent and affecting appearance). Type 3 Type 3 gemstones are stones that will almost always have inclusions. An example of such group is emerald or red tourmaline. Clarity in the type 3 group of gemstones are classified as VVS (noticeable), VS (obvious), SI1 (prominent), SI2 (more prominent) or I (affecting appearance or durability). |
