Australian opal, a truly rare and treasured gem, is predominantly sourced from the unforgiving landscapes of the Australian outback, where unique geological conditions have fostered the formation of opal deposits near an ancient inland sea.
Opal, a dazzling jewel, presents a kaleidoscope of colours ranging from deep blues and vivid greens to shimmering golden oranges; from soft pinks and violets to rich turquoise, vibrant vermilions, crimsons, and fuchsias—a magnificent spectrum of hues.
Australian opal can exhibit an array of vibrant colours intricately arranged in captivating patterns such as harlequin, pin-fire, Chinese writing, flower garden, mackerel sky, flagstone, and rolling flash. Like all exceptional treasures, gem-grade opal is exceedingly scarce.
Australia is renowned as the premier source of opal, revered for producing some of the world's most exquisite, rare and expensive specimens. In 1994, opal was officially designated as Australia's National Gemstone.
Opal can also be found in various other countries, including Brazil, Mexico, Ethiopia, the United States, Canada, Peru, Indonesia, Honduras, Slovakia, and the Czech Republic. Each location yields a distinct type of opal, and in forthcoming blog posts, we will feature images and information about these different varieties of opals. Stay tuned for an exciting journey ahead.
Colour and formation
What contributes to opal's mesmerising hues?
Opal comprises minuscule spheres of silica dioxide—so tiny that they can only be spotted through an electron microscope. In precious opal, renowned for its spectral colours or "play of color", these silica spheres are uniform in size, arranged in precise rows and layers. This meticulous arrangement forms structures that refract white light into a spectrum of captivating colours. The smallest spheres yield violet-hued opal, while the largest evoke radiant red tones, with sphere size ascending from violet to red across the spectrum.
The majority of opals lack the play of color and are classified as common opal or potch. Common opal typically presents in shades of gray, black, white, or amber, although it can be found in various other hues. While common opal also contains silica dioxide spheres, these spheres are irregular in shape, size, and arrangement.
How is opal created?
Opal crystallises when silica-rich water infiltrates cavities and voids in rock or clay, leading to the gradual evaporation of water and the formation of microscopic silica dioxide spheres. The precise combination of pH levels and other chemical factors necessary for opal formation is exceedingly rare and occurs less frequently in nature.
Value and Rarity
What accounts for the premium price of Australian opal?
Australian opal, also known as precious opal, stands as a coveted gemstone alongside rubies, emeralds, and diamonds. The rarity of Australian opal contributes to its high cost, as the process of prospecting and mining for this exquisite gem demands significant investment. Countless miners search for months, utilising costly equipment and expending substantial sums on fuel, with the hope of uncovering just a single exceptional opal, or perhaps a few. Thus, if you want to acquire a high-quality opal be prepared for considerable expenses that reflect its true worth.
It is essential to note that while some opals command high prices, there exists a diverse range of opals to suit every budget. If one can afford an ice-cream one can definitely afford a common opal.
How rare is Australian opal?
Although silica is abundantly present on Earth, the occurrence of precious opal is exceptionally rare, surpassing even the rarity of diamonds. The scarcity of precious opal can be attributed to the infrequent natural processes that give rise to this captivating gem.
The vast majority (at least 95%) of opal unearthed by miners is common opal lacking the vibrant colours characteristic of gem-quality opal. Known as potch opal in Australia, it can display hues of white, grey, black, or amber. Even when miners discover gem-quality opal, a significant portion may prove unsuitable for cutting into gemstones due to its thinness or sandy composition.
Varieties of Opals
What defines black opal?
Black opal stands as the rarest and most esteemed form of opal, characterised by a dark or black body tone. These opals exhibit a stunning array of colours, spanning the entire spectrum. The dark body tone of black opals enhances the richness and intensity of the colours displayed on the gem's surface.
If you ignore the colour in an opal, how dark is its body tone? A gem with a black or near-black body tone is classified as a black opal, while opals showcasing a dark yet not entirely black body tone are known as dark opals.
What distinguishes light opal?
Light opal features a delicate body tone, imparting a soft and pastel-like quality to the colours present in precious light opals. The lightest variations of light opal are sometimes referred to as white or milky opals.
Exploring crystal opal
Crystal opal has got a translucent quality, allowing light to penetrate through the gem when illuminated from behind. Unlike amethyst or diamond, crystal opal lacks a crystalline structure; its designation as "crystal" originates from its transparency, resembling crystalline materials like rock crystal or glass. Australian crystal opal, when backlit, emanates a warm orange hue.
While most crystal opals exhibit a light body tone, some may mirror the dark allure of black opals, earning the title of Black Crystal.
Unveiling boulder opal
Boulder opal features opal sections set against a natural backdrop of host rock. Among the most renowned boulder opals originate from Western Queensland, where opal formations occur within cavities of ironstone—a brown-hued, iron-rich rock.
When opal layers rest upon dark ironstone, they exhibit vibrant colours and a deep body tone akin to black opal. Occasionally, opal is dispersed in thin, irregular veins throughout the ironstone, known as boulder matrix.
Boulder opal regions also yield thicker 'pipes' of crystal opal, shaped by the infilling of cylindrical cavities left by burrowing invertebrates, tree roots, or fallen branches - fossils.
What is potch opal?
Potch opal shares the same mineral composition as opal—microscopic spheres of silica dioxide. The key distinction lies in the arrangement of these spheres: while precious opals showcase an orderly layout akin to oranges neatly stacked in a crate, potch opal features a jumbled configuration.
Appraising Opals
How is the value of opal determined?
Similar to other gemstones, the primary unit of evaluation for opal is the carat, a standard weight measurement. Opals are priced per carat, with one carat equivalent to 1/5 of a gram.
The pricing of opal per carat is influenced by a variety of factors:
- Brightness - Optimal brilliance is the main goal
- Color - Purple is commonly found, followed by blue, green, gold, orange, and the rarest and most highly prized red
- Pattern - Intricate patterns like Chinese Writing or Harlequin are more scarce compared to others such as Pinfire
- Body Tone - The body tone refers to the opal's darkness when considering color; generally, the darker the body tone, the rarer and more valuable the opal
- Consistency - Opals exhibiting uniform brightness and beauty from all angles command higher value than those with inconsistent appearances
Additional considerations encompass imperfections like visible sand or potch on the opal's surface.
In essence, the more unique and rare the combination of characteristics present in a precious opal, the greater its value. Just as with fine art, exquisite wines, or other exceptional jewels, personal preferences and market dynamics can also influence the final price.
Our passion for Australian Opal
At Mia and Stela Jewelry, our fascination with Australian Opal began long ago, capturing our hearts with its unparalleled beauty and distinctive qualities. The discovery of its unique characteristics, charm, and authenticity inspired us to curate a collection dedicated to this magnificent gemstone.
As you are aware, Australian Opal is renowned for its rarity, with each stone possessing its own individuality. Therefore, the majority of the jewelry featuring in our Australian Opal Collection are crafted as exclusive limited edition pieces. We also invite you to connect with us through our Contact page to explore our exquisite collection of loose Australian Opal stones, select the gem that resonates with you, and embark on the creation of a bespoke jewelry piece destined to be cherished for a lifetime.
