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How To Choose a Quality Opal

The birthstone for October, the opal has a rainbow of colors and a fiery iridescence that sets it apart from other gemstones. Like other gems, though, there are things you need to know to determine their quality.


  • TIP: Opals are relatively soft stones prone to developing cracks if not properly stored and maintained.
  • Step 1: Know that opals, like other gemstones, are measured by weight in carats. The larger the opal, the more it is worth.
  • Step 2: Buy from a reputable opal dealer. If you're making a significant investment, ask for a certificate of authenticity outlining the opal's properties.
  • FACT: The ancient Greeks believed opals gave their owners the gift of prophecy.
  • Step 3: Watch out for faults, like inclusions, which are mineral deposits inside the opal and devalue the stone. If an opal has crazing -- fine lines and fractures -- it will likely crack in heat or dry conditions and is virtually worthless.
  • Step 4: Expect to invest heavily in an opal that boasts a distinct pattern, with names such as the peacock tail, jigsaw, or harlequin, which are extremely rare and extremely expensive.
  • TIP: Doublets and triplets are partially man-made opals and are less valuable.
  • Step 5: Look for the play of color in the stone. Generally, the more colors it has, the more valuable it is. Some colors are considered more valuable than others, too, with red topping the list, followed by orange, yellow, green, and blue.
  • TIP: The most valuable opals will have the least "dead" or white spots.
  • Step 6: Pay attention to the stone's brilliance. An opal may have lots of color, but if it's dull, it'll be less valuable. Inexpensive white stones may have no noticeable flashes of color at all. Bright flashes of color in a stone indicate how much light it's reflecting and indicate higher quality, even if it only has a single color.
  • Step 7: Determine the type of opal, based on its background color. Black opals, which have a range of dark-colored backgrounds, are the most expensive. Crystal opals, which are transparent and highly reflective, are the second most valuable type, followed by the more common white or milky opals, which are not as reflective. Other types include the fire opal, boulder opal, and matrix opal.

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