Opal's play-of-color has long captivated humanity, the shifting display of colors telling each gem's unique story.
Opal is a gem unto itself, forming from deposits of silica that have filled rock over thousands or millions of years. Water would carry the silica to the stone. As the water dries, the silica would remain. The ordered structuring of these deposits is what provides opal its unique and fascinating play of color. They stack in relatively neat rows and columns, dispersing light to show various colors throughout the gem. The difference in size of these individual spheres of silica is what produces the different colors that are seen throughout this gemstone.
A wide variety of colors are available when considering opal gems, and they can occur in white, blue, green, yellow, red, and black varieties. The color of this part of the gem is called bodycolor, and many of the finest specimens have a dark bodycolor, with black often being preferred to best show the play-of-color, the refraction of light within the gem for which opal is most known.
The play-of-color of opal is a factor in determining a gem's value as well. Ideally, the play-of-color will display all the colors of the rainbow evenly across the stone. However, this isn't usually the case. Some opals may only show the color play in patches on parts of the gem. Sometimes, only certain colors may display. The most coveted display colors are red, orange, and green – in that order.
The clarity of an opal is regarded according to the type. In some varieties, transparency is more desirable. In others, an opaque bodycolor is preferred. Generally speaking, dark colored opals are preferred to have an opaque body color while lighter colored opals are preferred with more transparency, primarily due to how the colors best display in each variety.
No discussion of clarity is complete without also covering the potential for inclusions. Opals can show any of the typical inclusions that can be found in other gems. And there are two kinds of inclusion more common to this gem. Some opals can contain fragments of their host rock, known as matrix. It depends on the variety of opal, but this usually reduces the value of the gem. Opals are also susceptible to an inclusion known as crazing. As opals retain moisture, they can sometimes dry over time. When this happens, tiny fractures can develop within the gemstone. These fractures are called crazing.
It's most common for opals to be shaped into oval cabochons, as this shape best preserves the play-of-color within the gemstone. Varieties of opal that are highly transparent may be faceted into commonly found fancy cuts. Opals may also be fashioned into beads if they are lower quality material. High-quality examples may be shaped into custom forms so that the play-of-color is best preserved. These often go on to be set into unique jewelry pieces by top designers.
On occasion, opals may undergo a treatment process. When an opal is treated, it is usually constructed into a doublet or a triplet. An opal doublet is an opal gem that is placed onto a backing material. Typically, this both strengthens the gemstone and also improved the play of color by selecting a dark backing material. Thinner segments of opals are often fashioned into triplets. A triplet starts by following the same process as a doublet. Applying a cap to the gem finishes it, constructed of crystal, quartz, plastic, or another transparent material. The cap protects the soft opal and also magnifies the opal specimen underneath so that the play-of-color is even more pronounced.
Australian boulder opal is most celebrated for its spectacle of rainbow-like hues, which vary with lighting or angle of observation. Not every opal has this rare color feature.
Australian white opal cradles a rainbow of flickering color spheres. Reflections of colors dance about with every angle and change of light.
The Ethiopian Welo opal displays the liveliest play of color and fire, and often this vivid frolic of colors infuse an entire piece.
Jalisco fire opal captures the glow of volcanic lava streams within which it formed. Venerated for its vibrant and passionate orange sparkle, this fiery gem is a favorite for collectors.
Because pink is a fashion favorite, Pink Opal is a gem that is much in demand. This pretty pink gemstone is rarely seen offered for sale in standard jewelry stores.
Also known as denim opal, the beautiful Oregon blue opal is celebrated for its depth of the color and subtle opalescent glow.
Also known as Andean opal, the beautiful Peruvian mint green opal is celebrated for its depth of the color and subtle opalescent glow.
Looking into a Peruvian Pink Opal is like looking into a pink cloud with tiny raindrops of color. The opal is celebrated for its spectacle of rainbow-like hues, which vary with lighting or angle of observation.
Opal opulence takes on a striking new hue with Sierra Madre purple opal. Luminous opal takes on a royal purple base color thanks to the presence of fluorite during the formation of this stone.
• Opal is the national gemstone of Australia.
• It is the birthstone for those born in October.
• It's believed that the world opal derives from the Roman opalus, itself arising from the Sanskrit word úpala.
• Opal was considered a stone of luck during the Middle Ages, as it carried the characteristics of all gems whose color it emulated.
There are several famous deposits of opal found all over the world, but more so than Australia. This country is often cited as the leader in the production of opal, well-known for several particular varieties, such as boulder opals. Ethiopia has risen as a world supplier of opals, with a new, high-quality deposit uncovered in 2008. Opals originating from this country are often compared to those from Australia. Mexico is particularly noted for its production of fire opal, especially from the Jalisco region. Opals have also been found in other notable locations, such as Brazil, Peru, and Oregon, in the United States.
• On average, an opal contains between 6-10% water.
• Opal ranks from 5-6.5 on the Mohs scale of hardness.
• The largest known opal is the Olympic Australis, weighing 17,000 carats (7.6 lbs)!
• The first synthetic opal was created in 1974, distinguishable by its rigidly ordered pattern.
• Australia's opal fields are larger than the rest of the world's combined!