Opal Facts

Australian Opals: A Gemstone’s Journey

Certainly! Here’s a more detailed history of opal discovery in Australia:

The story of Australian opals begins with the early expeditions of Johannes Menge, a German mineralogist. He is credited with discovering precious opal near Angaston in the Barossa Valley of South Australia in 1841

1. This marked the first known discovery of common opals in Australia.

Following this initial find, attention shifted to Queensland, where opal was discovered at Listowel Downs Station in central outback Queensland in 1869

1. The Queensland Boulder Opal and Lightning Ridge fields began to draw miners in the 1880s, with the production of precious opal commencing at White Cliffs in New South Wales in 1890
2. This was a significant development, as White Cliffs became the first commercial opal field in Australia.

Tully Cornwaith Wollaston, who travelled to the central Queensland fields in the summer of 1889, played a pivotal role in the industry. He is often referred to as the father of the Australian opal industry for his success in trading and marketing Australian boulder opals in London in 1890

1. His efforts helped establish the global reputation of Australian opals.

The town of Lightning Ridge in New South Wales, originally named Wallangulla, is renowned for its black opal. Opal mining began there when a boundary rider named Charlie Nettleton unearthed opal in 1902

1. Lightning Ridge black opal is now considered the finest in the world, with surrounding fields like Coocoran, Glengarry, and Sheepyard enhancing the region’s reputation.

In South Australia, the town of Coober Pedy is synonymous with opal mining. It’s situated on the edge of the Stuart Range, 838 kilometres north of Adelaide. The first opal discovery there was made by Jim Hutchinson and his team, who were prospecting for gold on behalf of the New Colorado Prospecting Syndicate. They found opal “floaters” after a thunderstorm at what is now known as one-tree hill or Treloars Hill. The first claim was pegged on February 9, 1915, by Hutchinson’s son Willie, who was just fifteen years old at the time

1. Since the late 1800s, Australia has been a dominant force in opal production, contributing to more than 90% of the world’s supply
2. The opal industry has not only been a source of beautiful gemstones but also a significant part of Australia’s mining history and cultural heritage. The opal fields of Australia continue to attract those seeking fortune and adventure, and the gemstone itself remains a symbol of Australia’s unique natural resources.

Opal formation is a complex process that occurs over millions of years and under very specific geological conditions. Here’s an extended and detailed explanation of how opals are formed:

1. Silica-Rich Solution Formation: Everything begins with rainwater, which seeps into the ground and passes through sandstone layers, dissolving silica from the sandstone. This results in a silica-rich solution, essentially silicic acid, that travels through the earth’s subsurface.
2. Filling Voids: The silica-rich solution finds its way into natural voids in the rock, which could be cracks, crevices, or spaces left by decomposing fossils. These voids are crucial as they provide the space where opal can form.
3. Evaporation and Deposition: As the water from the solution evaporates, it leaves behind a deposit of silica. This cycle of evaporation and deposition continues over vast periods, gradually accumulating layers of silica and eventually leading to the formation of opal.
4. Formation of Silica Spheres: In some cases, the conditions allow for the formation of tiny spheres of silica within the solution. These spheres can settle under gravity, forming layers. The rate of deposition is incredibly slow, with estimates suggesting a rate of about one centimetre of thickness every five million years at a depth of forty meters.
5. Precious Opal Development: For precious opal to develop, these silica spheres must be uniform in size and closely packed. The size of these spheres typically ranges from 150 to 400 nanometres. When they are uniform and closely packed, they diffract light, creating the opal’s characteristic play of colour in the visible spectrum, which ranges from 400 to 700 nanometers.
6. Variety of Opal Types: The type of opal formed can vary greatly depending on several factors. The climate, for instance, influences the formation process by providing alternating wet and dry periods, which affects the water table and the concentration of silica in solution. The source of the silica is also a factor; it can come from volcanic activity or from the deep weathering of sedimentary rocks. This leads to the formation of different types of opal, such as boulder opal, matrix opal, and others.
7. Potch Formation: Not all opal is precious; much of it is “potch,” which is common opal that does not show the play of colour. Potch forms when the silica spheres are not uniform in size or are not closely packed enough to diffract light.
8. Environmental Influence: The environment in which opal forms can also affect its characteristics. For example, opal formed in volcanic rocks tends to fill only vughs and cracks, while in sedimentary rocks, a variety of voids created by weathering processes can be filled with opal. This includes leaching of carbonate from boulders, nodules, and fossils, as well as existing cracks and seams, providing numerous Molds for opal deposition.
9. Matrix Opal: In some cases, the opaline silica fills the pore space in silt and sand-sized sediments, cementing the grains together. This forms unique deposits known as matrix opal, opalized sandstone, or “concrete,” which is often found near the base of early Cretaceous sediments.

Opals are significantly rarer than diamonds, and the figure of being 18,000 times rarer is often cited to emphasize this rarity. The rarity of opals compared to diamonds can be attributed to several factors:

Geographical Availability:

• While diamonds are mined in various countries around the world, high-quality opals are predominantly found in Australia, which produces over 90% of the world’s precious opals1. Ethiopia is another source of high-quality opals.

Quality and Gem-Grade Proportion:

• Although both diamonds and opals are common in their basic forms, the proportion of these that are of gem quality is much lower for opals1. Finding a high-quality opal, which displays a vivid play-of-colour and clarity, is much more challenging than finding a gem-quality diamond

Market Dynamics:

• The value and rarity of a gemstone are closely related to supply and demand. Diamonds, despite being more common, have a high demand that maintains their value. Opals, while less in demand, are valued for their rarity, especially the gem-quality stones that can fetch prices comparable to diamonds for their size and quality

Unique Formation Process:

• Opals are formed from a solution of silicon dioxide and water. This process takes place under specific conditions that are not as widespread as the conditions that form diamonds. The unique formation process of opals contributes to their rarity.

Variety and Uniqueness:

1. Each opal is unique, with a distinct pattern and colour play. The rarity increases for opals with unique characteristics and exceptional beauty, such as black opals or boulder opals with distinctive colour patterns.
2. In essence, the rarity of opals is not just about the frequency of occurrence but also the availability of high-quality, gem-grade opals that exhibit the desired characteristics that make them so prized in the gemstone market.

 

Australian Black Opals & Other Opals

Australian opals are renowned for their beauty and variety, with the black opal being the most valuable and widely known type. These opals are characterized by a dark body tone, which ranges from dark grey to jet black, enhancing the vibrancy of the colours within

• . The main source of black opals is Lightning Ridge in New South Wales.

Value and Rarity

The value of Australian opals is influenced by their rarity, quality, and the play-of-colour they exhibit. Top-quality gem black opals can fetch prices up to AUD $15,000 per carat1. Factors like brightness, pattern, and body tone determine the overall value of an opal2. Black opal is 5,000 times rarer than diamond, making it a highly sought-after gemstone.

Australian black opals are celebrated for their mesmerizing colour play and the rare patterns that can appear within them. These patterns are a result of the way silica spheres are arranged within the opal and can greatly affect the value of the opal. Here are some of the rare and sought-after patterns found in Australian black opals:

• Harlequin: This is the rarest pattern and is characterized by a mosaic-like, checkerboard appearance with broad, angular patches of color.
• Flagstone: This pattern displays a jigsaw puzzle effect with angular, interlocking areas of color.
• Ribbon: As the name suggests, this pattern shows colour in long, ribbon-like bands across the stone.
• Straw: This pattern looks like a field of straw or wheat, with thin lines of colour running parallel to each other.
• Chinese Writing: Resembling calligraphic characters, this pattern features short, intersecting lines of color.
• Pinfire: A multitude of small, closely set patches of colour, resembling pinpoints, defines this pattern.
• Rolling Flash: This pattern offers a large, shifting colour play that moves across the stone as it is turned.

The rarity of these patterns, especially the Harlequin, adds to the allure and value of Australian black opals, making them highly prized by collectors and enthusiasts around the world. The unique conditions at Lightning Ridge, where these opals are mined, contribute to the formation of such distinctive and captivating patterns.

Identifying a genuine Harlequin-patterned opal involves looking for specific characteristics that define this rare and valuable pattern. Here are some key features to look for:

• Pattern Definition: A true Harlequin opal displays a repeating pattern of contrasting diamonds or elongated squares.
• Colour Play: The pattern should present a spangled appearance, with a mosaic-like chromatic pattern in rounded, angular, or roughly square patches of about equal size.
• Body Tone: Ideally, a black opal with a body tone of N1 is the most sought after for the Harlequin pattern.
• Rarity: Genuine Harlequin patterns are extremely rare. Even among thousands of opals, only a few may exhibit a true Harlequin pattern.
• Value: Due to its rarity, a Harlequin-patterned opal can be quite valuable, with prices ranging significantly based on the quality and size of the pattern.

When assessing an opal for authenticity, it’s also important to consider the overall quality of the gemstone, including its brightness, colour range, and clarity. If you’re unsure about the authenticity of an opal, consulting with a professional gemmologist or a reputable opal dealer can provide additional assurance.

In addition to the Harlequin pattern, there are several other opal patterns that are highly valued in the gemstone market. Here are some of the valuable opal patterns:

• Pinfire: This pattern is characterized by small, closely spaced patches of colour that resemble pinpoints. It’s a common pattern but can be quite beautiful when the colours are vibrant.
• Rolling Flash: Opals with this pattern display large, shifting areas of colour that move across the stone as it is turned. It’s a dynamic and eye-catching pattern.
• Straw: Similar to the straw in a field, this pattern features thin lines of colour running parallel to each other. It’s a delicate and intricate pattern that is quite rare.
• Chinese Writing: This pattern looks like calligraphic characters and features short, intersecting lines of colour. It’s a unique and sought-after pattern.
• Honeycomb: Highly prized, especially in Ethiopian opals, this pattern resembles the hexagonal cells of a honeycomb and is known for its rarity and beauty.
• Broad Flash: This pattern has large flashes of colour that are predominant in the opal, creating a bold and striking appearance.
• Cathedral: Seen in Boulder opals, this rare pattern is mostly formed by wood or vegetation matter and has a distinctive look.

These patterns contribute to the opal’s overall value and appeal, with rarity, colour play, and brightness being key factors in determining their worth. Collectors and enthusiasts often seek out these patterns for their unique beauty and the craftsmanship required to reveal them in the finished gemstone.

Australia’s Share in the World Opal Market

Australia dominates the global opal market, supplying over 95% of the world’s precious opals3. This significant share is due to the country’s rich opal mining history and unique geological conditions that favour opal formation.

Differences Between Australian Opals and Others

Australian opals differ from those found elsewhere due to their vibrant colours and durability. They are less susceptible to changes caused by water or chemicals, as solid Australian opals like the White Opal and Black Opal are non-porous. In contrast, opals from other regions, such as Ethiopia, may be hydrophane, absorbing water and potentially altering their appearance.

The Future of Australian Opals

The Australian opal industry is experiencing a resurgence, with increasing demand both locally and internationally. The rarity of certain types of Australian opals, like the black opal, continues to drive their value in the market. With ongoing exploration and mining, the future of Australian opals looks bright, promising continued interest and appreciation for these natural wonders.

Certainly! Australia is famous for its diverse range of opals, each with unique characteristics and origins. Here’s a brief overview of the different types of Australian opals:

Black Opal

• Origin: Primarily mined in Lightning Ridge, New South Wales.
• Features: Known for a dark body tone which enhances the colour play. The term ‘black opal’ refers to the stone’s dark background, not necessarily the colour black.

White Opal

• Also Known As: ‘Milky opal’.
• Origin: Mainly found in South Australia.
• Features: Light white body tones and can display magnificent colours if of high quality, though generally not as vibrant as black opals.

Boulder Opal

• Origin: Forms on ironstone boulders in Queensland.
• Features: Often cut with the ironstone left on the back due to the thin opal seam. Can be very dark and beautiful in color.

Crystal Opal

• Features: Transparent or semi-transparent body tone. Can be ‘black crystal opal’ or ‘white crystal opal’ depending on the body tone’s darkness or lightness.

Matrix Opal

• Features: Occurs as a network of veins or infilling of voids or between grains of the host rock, such as ferruginous sandstone or ironstone.

Fire Opal

• Note: Not commonly used within Australia but refers to opals with a significant amount of red colouring, which is the rarest and most valuable.

These opals are not only a testament to Australia’s geological richness but also contribute significantly to the country’s cultural and economic landscape. Each type of opal has its own distinct beauty and appeal, making them highly prized by collectors and jewellery enthusiasts worldwide.

 

Australian opals are cherished not only for their physical beauty but also for their metaphysical properties. They are believed to have a special ability to promote spiritual, emotional, mental, and physical healing. Here are some of the metaphysical properties attributed to Australian opals:

• Spiritual Growth: Opals are said to enhance spiritual growth and development, connecting individuals to higher realms.
• Emotional Healing: They are thought to soothe the emotional body, bringing peace and tranquility.
• Mental Clarity: Opals may aid in boosting mental clarity and intuition, helping to bring buried emotions to the surface for examination and transformation.
• Physical Healing: Some believe that opals can contribute to physical healing by amplifying and returning thoughts and feelings related to the body’s state.
• Chakra Connection: Opals are associated with various chakras, depending on their colour, and are used to balance and align these energy centers.

These properties make Australian opals a popular choice for those interested in crystal healing and metaphysical practices. However, it’s important to note that while many people believe in these properties, they are not scientifically proven and should be approached as a complementary practice rather than a substitute for professional medical advice.