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Gem Adventurer Oval Cabochon 18 x 13mm Australian Boulder Opal Loose Gemstone

Earthy awesomeness! Found primarily in Australia, in large ironstone boulders, this gem is ultra durable and offers vibrant color. You'll even notice thin veins running throughout the stone, making it a pretty unique conversation starter. Whether you simply display this in your home or wear it as a piece of jewelry, it's sure to draw plenty of attention!

Stone Details

  • Gemstone: Australian Boulder Opal
  • Shape/Cut: Oval Cabochon
  • Measurements: 18 x 13mm
  • Collection: Gem Adventurer
  • Country of Origin: Australia

About Australian Boulder Opal

Created when opal fills cracks and crevices in ironstone boulders, Queensland Boulder Opal is a unique variety with attractive 'play of color' flashes sparkling on the surface of the contrasting ironstone host rock, which also provides excellent durability. Unique to opal, 'play of color' is the attractive flashes of colorful brilliance that change with the angle of observation. Opals are classified by their host rock (also known as 'potch' or 'matrix') on which opal forms and their resulting transparency and body color (the base color on which opal's color play is visible). When cut, most Boulder Opal includes the host chocolate brown ironstone. This results in striking, irregular patterns, making each gem unique. Skillful lapidary is critical for Queensland Boulder Opal and each gem has been cut with a desirable finish, proportion, shape, and symmetry.

Opal is from the Greek 'opallios', meaning 'to see a change'. While opal has been Australia's national gemstone since 1993, it has been part of indigenous culture for over 60,000 years. Dreamtime legends passed down by storytellers call Opal the 'fire of the desert', describing how their ancestral creator came to earth on a great rainbow, which turned the rocks it touched into resplendent Opals.

Australia's opal fields might be the largest in the world, but only 25% of Australian opal mined is gem-quality. Discovered in 1869, Queensland Boulder Opal occurs sparsely over a huge area of the Australian state of Queensland centered on the town of Quilpie (pronounced Kwill-Pee), but extending to Winton in the north and Cunamulla in the south. Recent years have seen dramatically lower production levels for Queensland Boulder Opal with output decreasing by 50% in the last 10 years due to the depletion of commercially viable areas and mounting operational costs.

A relatively durable jewelry gemstone, Queensland Boulder Opal has a Mohs Hardness rating of 5.5 - 6.5 and should always be stored carefully to avoid scuffs and scratches. Clean with gentle soap and lukewarm water, scrubbing behind the gem with a very soft toothbrush as necessary. After cleaning, pat dry with a soft towel or chamois cloth.

Why Buy Loose Gemstones?

As gem mines are becoming more and more depleted, gemstones of all types are becoming increasingly sought-after. Whether you are a collector or a first-time buyer, you will be amazed by the timeless glamor loose gems have to offer! They are fun to collect and look spectacular no matter how you display them. You can make an appointment with your jeweler to experience the joy of creating your very own, one-of-a-kind design. Choose from a variety of settings and styles to create a completely unique presentation that's sprung from your own imagination. Or display your loose gems under glass, showcasing rare and vibrant stones in an artistic and sophisticated manner. No matter how they're displayed, loose gemstones are brilliant collectibles for gem lovers and avid collectors alike!

All weights pertaining to gemstones, including diamonds, are minimum weights. Additionally, please note that many gemstones are treated to enhance their beauty. View Gemstone Enhancements and Special Care Requirements for important information.

LooseStones    Opal    
Gemstone Glossary

Cut: Refers to the geometric shape and proportions of a gemstone. A gemstone’s cut is what most directly affects its sparkle or brilliance.

Facet: A flat cut on the surface of a gemstone.

Fire: Flashes of rainbow colors. Also called “dispersion.”

Hardness: Resistance to scratching. The higher the number, the more resistant.

Hue: Another word for color.

Luster: The shininess of a jewel.

Opaque: The opposite of transparent. Light cannot pass through an opaque gemstone, therefore they do not have any sparkle or fire.

Saturation: This term refers to how pure or deep a gemstone’s color is. Some gemstones, like aquamarine, have a naturally low saturation (very light blue) while other gemstones, like amethysts, can have very high saturation (rich, dark purple).

Sparkle: The white light leaving a jewel, traveling upward, which is visible to the eye. Sparkle is often referred to as “brilliance.”

Toughness: Resistance to breakage.

Gemstone Shapes & Cuts
These are the common shapes or cuts for gemstones, each lending a different look and allure.

Baguette: Baguette means “stick” or “rod” in French, which makes it a very appropriate name for this gemstone shape. Diamond baguettes are often used as accent stones to flank a primary stone.

Brilliant: Any gemstone cut with 58 facets, which produces the maximum possible sparkle. A brilliant cut can have several shapes, including round, oval, pear, radiant and heart.

Cabochon: This shape features a rounded, perfectly smooth surface instead of facets. It is the oldest gemstone shape and is commonly used with opaque stones such as opal, jade and turquoise.

Cushion: A very popular style for most of the 19th century, cushion shapes are slightly domed with rounded corners that make the stone look like a pillow. In fact, this shape is often referred to as a “pillow cut.” It looks particularly beautiful in candlelight.

Emerald: With its long, steep facets, emerald cuts tend to flash rather than sparkle.

Fancy: Technically, this term refers to any type of gemstone that isn’t round, but many jewelers reserve it to describe the more exotic gemstone shapes such as marquise, heart, pear and trillion.

Heart: Often described as a custom cut, heart-shaped gemstones are very popular for pendants.

Marquise: According to legend, this shape was commissioned by King Louis XV to resemble the smile of his mistress, Marquise de Pompadour. Ideal marquise cuts have a length to width ratio of 2:1.

Oval: Similar to the round shape, oval gemstones produce a high amount of sparkle and fire.

Pear: This is a classic teardrop shape that is ideal for earrings and pendants.

Princess: This a relatively new shape that combines the sharp, flat edges of an emerald shape with numerous small facets, which produce both sparkle and fire.

Radiant: This shape is similar to emerald, but it adds extra facets on the edges and corners to increase the gemstone’s sparkle.

Round: This classic shape produces maximum sparkle and fire, making it an ideal shape for diamonds.

Tapered Baguette: A tapered baguette is a baguette shape with one end that is narrower than the other.

Trillion: A very striking, usually three-sided shape, trillion gemstones (especially diamonds) are celebrated for the intense fire they produce.

The Mohs Scale
The most common measure of a gemstone's degree of hardness is based on the Mohs Scale. Devised by German geologist Friedrich Mohs in 1812, the Mohs Scale grades minerals on a comparative scale from 1 (very soft) to 10 (very hard).

Hardness is generally associated with durability and the ability to resist breakage. When referring to gemstones, however, hardness more accurately means the stone's ability to resist abrasion. What the scale means is that a mineral of a given hardness rating will scratch other minerals of the same rating, as well as any minerals of a lower hardness rating. For example, rubies and sapphires, which are composed of the mineral corundum and have a Mohs rating of 9, will scratch each other, as well as topaz (rating 8) and quartz (rating 7). But they will not scratch diamonds, which are rated 10 and considered the hardest substance.

The numeric values assigned to each interval of hardness are not equal. Some stones are disproportionately harder than others. Because Mohs Scale wasn't made for exact precision, it uses half numbers for in-between hardness ratings.

Opal
Known for its fiery combination of colors, opal is called the "Cupid stone" because it was said to reflect the complexion of the Greek god of love. The ancient Romans believed the gem was the symbol of hope, good luck and purity. Today, it remains a symbol of hope and inspiration. With a name stemming from the Latin word for "precious stone," opal is considered October's birthstone and is traditionally given as a 14th anniversary gift.

Opals are luminous and iridescent stones with inclusions of many colors called "fire." It is sometimes called the "queen of gems" because it can flash patterns of color representing every hue of the rainbow. In fact, most stones are usually cut into domed cabochons to enhance the color play. The brilliance and pattern of an opal's fire determines its value. Opals with strong flashes of red fire are generally the most prized, while stones with blue or green flashes are more common and subsequently less valuable. Stone size also helps determine price, since the gem is very rare in larger sizes.

In order to produce a stone that is less expensive than a solid opal, an opal doublet can be manufactured. It is composed of a thin layer of opal glued on top of another mineral (usually a black onyx or ironstone, which enhances the opal's color). An opal triplet can be made with a thin layer of opal sandwiched between a layer of clear quartz on top and a layer of obsidian or ironstone on the bottom. The clear quartz top layer makes the gem harder and less susceptible to scratches. Since top-quality natural opals are extremely rare and expensive, many are treated with colorless oil, wax or resin to enhance their appearance. Ranking a hardness of 5.5-6.5 on the Mohs Scale, these treatments also fill cracks in the stone to improve durability.

A species of quartz, opal is one of the few gemstones that are sedimentary in origin. Millions of years ago, after ancient seas receded, silica-laden sediment was deposited around shorelines. Erosion made much of this silica into a solution that filled cracks in rocks, clay and fossils. Layers upon layers of silica jell were added to each other over millions of years and became precious opals. The stones still contain 6 to 10 percent water, a remnant of ancient seas. Because they have high water content, opals should be protected from heat and strong light in order to prevent them from drying out and cracking.

Opal is found in a range of hues, including white opal (the most common), black opal (the most valuable), boulder opal (black opal with iron oxide), crystal or water opal (which is transparent), and fire opal (which features a bright solid color). The body color determines the variety of opal and has a large impact on the value.

White opals tend to have more diffused fire due to their light background color. Rare black opals have a black to dark gray body color that allows for the fire to be the most noticeable, making them the most valuable type of opal. Boulder opals are cut with the natural host rock left on the back. They are found with interesting hills and valleys on the surface and inclusions in the foreground, forming odd shapes that make them a designer's delight. Crystal opal is transparent with flashes of rainbow colors, while fire opal only occasionally has this play of color. Fire opal's backdrop color is the main attraction. With bold yellows, oranges or reds, it is usually faceted to add sparkle and enhance the fabulous color.

The vast majority of the world's opal supply comes from Australia, first discovered there by gold panners in 1863. In addition to a small quantity of opal produced in Kenya and Canada, white opal is mined in Brazil, black opal is found only at Lightning Ridge in Australia, crystal and fire opal can be found in the United States and Mexico, and a blue-green opal is found in the Andes Mountains of Peru.

Opals have been treasured for thousands of years throughout the world. The gem was loved and highly valued by the Romans, who called it "opalus." In fact, a beautiful opal called the "orphanus" was featured in the crown of the Holy Roman Emperor and was said to guard the regal honor. The Aztecs mined opal in South and Central America and archaeologist Louis Leakey found 6,000-year-old opal artifacts in a cave in Kenya. Napoleon gave Josephine a beautiful opal with brilliant red flashes called "The Burning of Troy," making her his Helen. To this day, opals are still set in the crown jewels of France. Queen Victoria loved opals and often gave them as wedding gifts. She was one of the first to appreciate opals from Australia and, along with her daughters, created a fashion for wearing the gemstone.

There are also several literary references to the fascinating stone throughout history. Shakespeare regarded opal as a symbol of shifting inconstancy, comparing its play of color to play of mind. In "Twelfth Night" he wrote, "Now the melancholy God protect thee, and the tailor make thy garments of changeable taffeta, for thy mind is opal." In the 19th century, Sir Walter Scott caused a reputation that opals were unlucky. The heroine of his popular novel had her life force caught in the opal she wore in her hair and died when its fire was extinguished.

For thousands of years, opals have been revered for their supposed mystical powers. Romans thought the stone kept the wearer safe from disease and wore it near the heart on necklaces to ward off evil and protect travelers. Ancient Arabs believed that opals fell from heaven in flashes of lightning, which explained their fiery colors. During the Middle Ages, opal was called "ophthalmios," meaning "eye stone," due to a widespread belief that it was beneficial to eyesight. Some thought its effect on sight could render the wearer invisible, and the stone was even recommended for thieves. In medieval Scandinavia, blonde women wore opals in their hair to prevent it from going grey.

Today, opals are still believed to hold magical powers. White opals, when used in rituals on a full moon night, are said to bring the moon goddess' powers into full effect within the practitioner. Specially shaped black opals are often worn on gold jewelry to further enhance their magical properties and powers. A fire opal surrounded with 10 or 12 diamonds and worn on a gold necklace is said to have excellent money-drawing power.

Opals have been said to bring good luck, grant vigor and ideally protect travelers. The stones have long been believed to develop and increase mental capacities and open the unused powers of the mind. The colorful fire in opals is said to develop a more creative imagination and help recall past lives. It is believed that the most magically powerful opals come from Lightning Ridge in Australia and that the gem loses its power once its owner dies.