Gemstones come in many different colors; blue, pink, green, or red hue, a medium to medium-dark tone, and saturated color.
Flawless gemstones are very rare and valuable. Almost all gemstones contain tiny fractures called inclusions, and even the most high-end gemstones are at least slightly included.
The carat weight of a gemstone is not necessarily an accurate gauge for gemstone size. A more accurate gauge of the size is the diameter of the gemstone that is visible after it is set in the jewelry.
Almost all gemstones have had some kind of enhancement done to them, like heating, and are accepted in the jewelry industry as a part of the polishing and finishing policy. Gemstones that have not been enhanced are easy to recognize due to the extravagant price they command.
Natural pearls are very rare. Only in one of every 10,000 oysters, might you be lucky enough to find a single natural pearl. Because of this scarcity, most pearls today are cultured pearls. Pearls are graded and categorized in 5 main categories; color, luster, shape, markings and size.
Body-color is the term used to describe the general color of a pearl. Pearls typically come in cream, yellow, pink, white, silver, or black. Because some pearls have overtones of a secondary color, they may appear in different colors when light reflects off the pearl’s surface.
Pearls produce an intense, deep shine called luster. This effect is created when light reflects off the many layers of tiny calcium carbonate crystals that compose the pearl. The larger the pearl, the more calcium carbonate crystals, or nacre, it will have, giving it more luster. When selecting a pearl, consider that the larger the pearl the more luster it will have.
The rarest pearl shape is round. Shapes that are not spherical or even symmetrical are considered lower quality. Other pearl shapes are oval, off-round, and teardrop.
As a pearl is created in the oyster, spots and bubbles can develop in the layers of nacre. The pearls with the smoothest surfaces are the most desirable and the most expensive.
Freshwater pearls range in size from about 3.0–7.0mm, Akoya pearls range from about 6.0–8.5mm, and the South Sea and Tahitian pearls can reach sizes as large as 13mm.