Glossary - O
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- Off-Round Pearl
- Pearls that show more than a 2% variation in their circumference are considered off-round.
- Onyx, Black
- The common term for banded black chalcedony quartz, black onyx can be carved into cameos, shaped into cufflinks, and a wide range of other jewelry. Its color ranges from translucent to opaque.
- Opal
- This gemstone is composed of hydrated silica spheres which create a pattern of mini rainbows throughout the stone. It is also the birthstone of October. Because it is a relatively delicate gemstone, avoid sharp blows to your opal and keep it away from extreme heat. Opals have a 2-6% water content, so they should always be stored in a cool, protected place.
- Opaque
- Description of a gemstone that blocks light from passing through. It could be due to the number of inclusions or flaws, or it could simply be a characteristic of the gemstone; opals, for example, exhibit varying degrees of opacity.
- Opera Length
- A pearl necklace 32 inches long
- Orient
- The prismatic, rainbow-like effect that seems to encircle a pearl's surface.
- Oval Diamond
- Oval diamonds are very popular and range in shape from nearly round to very elongated. A longer oval shape can accentuate long, slender fingers.
- Oval Pearl
- Freshwater cultured pearls that are ovoid in shape
- Overtone
- A hint of a secondary color in the color of a pearl, typically pink, silver, or blue.
