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Opal, the October Birthstone


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Opal Characteristics:

Precious opal is a gemstone that exhibits flashes of rainbow-like colors when viewed from different angles. The colors are created by an arrangement of silica spheres within the opal.

Common opal does not exhibit a flash of color.

Opal Colors:

The opals we see most often in jewelry have a milky-white base with varying flashes, but other types of opals exist, too. The gems can have a light or dark body color and may be either translucent or transparent.
  • Black opals are the most rare and expensive versions of the gem, with a body color that can range from dark grey to black, and with fiery flashes of color.

  • Precious fire opals are another unique choice, and you'll find that variety with transparent or translucent base colors ranging from yellow to orange, with fiery flashes.

How Hard Are Opals?:

Opal hardness varies, but it generally ranges from 5.5 to 6.5 on the Mohs scale. Compare that to diamond, which is rated at 10, and is the hardest gemstone.

Treat Opals with Care:

  • Do not use harsh cleansers to clean your opals and do not place opals in ultrasonic cleaners.
  • Never rub oil on an opal, because although it makes the fire brighter, oil can damage the stone.
  • Some jewelers recommend that you periodically soak opals in water to help them reabsorb lost moisture.

Where Are Opals Mined?:

Australia is the leading source of opals, but a great number of fire opals are found in Mexico. Other sources of precious opals include Africa, the United States, Brazil, areas of the former Soviet Union and Nicaragua.

What Are Opal Doublets and Triplets?:

Opal doublets and triplets are composite stones that are made by positioning a thin layer of opal on top of a chunk of glass or less expensive gemstone.

Inspect the sides of an opal, looking for indications that it's really layered slices. Check the stone's base to see if it matches the top. If it doesn't, the stone might be a composite.

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