Colorful opal, appropriate for fall. The shifting play of kaleidoscopic colors is unlike any other gem.
Each opal is unique in pattern, shape, color, and type, making for one of a kind jewelry. Although it is only 5.5 – 6 on the Mohs Hardness scale, opal makes a beautiful jewelry gemstone.
The opal is a hydrated amorphous form of silica. As such, its water content may range from 3 to 21% by weight, but is usually between 6 and 10%. The internal structure of precious opal makes it diffract light. Depending.on the conditions in which it formed, it can take on many colors. Black opals are the rarest, white and greens are the most common. Opal is the national gemsotne of Australia.
Gem opals can be classified into four groups, light, dark, boulder, and black.
Light Opal, the most common, has a translucent milky to opaque white background. Crystal Opal is transparent to translucent. Fire Opal, a type of crystal opal, is reddish orange to red, is normally translucent to semi-translcent, and is found in Mexico and Ethiopia.
Dark Opal is opaque with a gray body color.
Boulder Opal contains sandstone or ironstone. Opal with matrix show visible ironstone. Opal with no visible inclusions is called opal in matrix. Most Boulder Opal is found in Queensland, Australia.
Black opal is opaque and very dark in body color. They are the most brilliant and often the most coslty because of their rarity and intense color. Most of these opals are from Australia.
Mexican Fire Opal is a type of crystal opal that shows magnificant flashes of red/orange color. Unlike most opals, fire opal is usually faceted so that you get sparkle in addition to vibrant color. Fire opal was born in fire in the ancient volcanoes of Mexico. It forms when water seeps into silica-rich lava, filling seams and hollows. Under heat and pressure, the silica forms a solid gel that traps the remaining water within its structure. Fire opal that displays play-of-color is rare because volcanic opal forms relatively quickly and the spheres of silica rarely have time to settle into the diffraction grids that create play-of-color.
Ethiopian opals originate from volcanic activity. All volcanic opal is called “hydrophane opal.” The term hydrophane comes from the Greek words meaning “water-loving” and describes their ability to absorb water and change from opaque or semi-translucent to translucent or transparent. Sometimes this highlights the color play – other times the opal will become transparent or opaque, with no color when hydrated. The color returns when the gem dries out.
It is important that you handle and clean your opal jewelry with care. Never use a steamer or ultrasonic, keep away from harsh temperatures or sudden temperature changes. Simply wipe your opal jewelry with a clean soft cloth.
The opal is a favorite gemstone of mine given its wide palette of colors, shapes and versatility in jewelry. I’ve created many pieces of opal jewelry over my 40-year career as a fine goldsmith. It also explains why we pride ourselves on having a wide selection of loose opals available to collectors and for custom jewelry orders.