Spotlight on October’s Birthstones: Opal and Tourmaline

People with October birthdays have the gift of choice when it comes to their birthstone. This month is traditionally associated with two birthstones: opal and tourmaline. Unlike some other gemstones, both of these minerals present a range of colors and features that make can make one stone quite different from another.

Spotlight on October Birthstones Opal Tourlamine | Auction King

Opal is a gemstone-quality variety of silica that is prized for its play-of-color, the flashes of colors you see when you turn an opal back and forth under white light. This phenomenon is caused by the refraction of light between the different layers of silica spheres that make up the stone. Given that opal can have a base color from white to black and play-of-color in literally any color of the rainbow, it is no exaggeration to say that no opal is exactly like the next. These stones are associated with good luck in many cultures, and have been prized since ancient Roman times.

Opal is a relatively soft stone, with a hardness of only 5 to 6.5 on the Mohs scale, so you’ll want to treat this gem with care and avoid exposing it to high temperatures, abrasion, or chemicals. The value of an individual opal, while it can be affected by considerations like size and clarity, is really based on a subjective judgment of the colors and patterns in that particular stone, and how well its cut displays them. Stones with less common play-of-color hues, such as reds, or bolder patterns featuring bright strokes of color are valued more highly than those with common colors and less vivid displays.

Tourmaline is the name given to a variety of boron silicate minerals that can be found in a rainbow of colors, depending on the amount and type of trace minerals found in the crystal structure. While it can occur in all colors, you’re most likely to find gems in pink, red, blue, green, or multicolored—yes, a single tourmaline can display multiple colors, depending on the conditions of its formation! With a Mohs hardness of 7 to 7.5, tourmaline is a relatively durable stone that is suitable for use in all types of jewelry.

Before the advent of modern gemological analysis, tourmaline was often mistaken for other gemstones, based on color. The different varieties of tourmaline may be referred to by names based on their color, such as rubellite for red or indicolite for blue. The color of a tourmaline is the most important factor in judging the quality of a tourmaline—unusual or highly saturated colors will command a higher price than more common or lighter types. For example, rare paraiba tourmalines, first discovered in Brazil in the 1980s, display a vivid blue-green, and are highly sought after.

No matter what kind of opal or tourmaline you’re looking for, AuctionKing.com routinely offers a variety of rings, pendants, necklaces, bracelets, and earrings—even loose stones. We continually add new items to our collection to ensure that our clients have a stunning selection to choose from. Sign up for a free online account and start browsing today.

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