Australian Opals: A Comprehensive Guide

Australian opals are among the most exquisite gemstones in the world. Known for their vivid play of color, these rare gemstones display a mesmerizing array of colors. They are popularly used in many different types of jewelry worldwide.

Opal is found in many different countries around the World. These include Brazil, Ethiopia, Mexico, Honduras, America and Australia. Australia is the world’s largest producer of opals, accounting for over 95% of global supply. Australian opals are particularly sought after in the gemstone market for their  color intensity, diversity, and rarity. Among them, black opals from Lightning Ridge, white opals from Coober Pedy, and boulder opals from Queensland stand out as the most popular types of Australian opals.

INDEX

1. What are Australian Opals?

Australian opals are among the most exquisite gemstones in the world. Known for their vivid play of color, these rare gemstones display a mesmerizing array of colors. They are popularly used in many different types of jewelry worldwide.

Opal is found in many different countries around the World. These include Brazil, Ethiopia, Mexico, Honduras, America and Australia. Australia is the world’s largest producer of opals, accounting for over 95% of global supply. Australian opals are particularly sought after in the gemstone market for their  color intensity, diversity, and rarity. Among them, black opals from Lightning Ridge, white opals from Coober Pedy, and boulder opals from Queensland stand out as the most popular types of Australian opals.

2. How Were Opals Formed?

Opals were formed over millions of years under unique geological conditions. Around 100 million years ago, much of central Australia was covered by a vast inland sea, known as the Eromanga Sea. As the sea receded, it left behind a sedimentary basin rich in silica. This area is known as the Great Artesian Basin. Water containing dissolved silica seeped into cracks and voids in the ground; often in fossils, decaying wood, or ironstone rock.

The Eromanga Sea /Great Artesian Basin and locations of Opals found in Australia

Over time, as the water evaporated, it left behind layers of silica that gradually hardened into opal. Silica spheres structured in a grid like formation are the basis of creation of both common and precious opal. The process is delicate and rare, requiring very specific environmental conditions. This explains why high quality opal deposits are so limited in geographic distribution, making Australian opals not only beautiful but also geologically precious. Due to the amount of time it takes to create such beautiful gemstones, they cannot be reproduced by man without interference of plastics and other chemicals involved. These recreations are known as synthetic opals.

A natural Australian Dark Opal vs Synthetic Opal

3. The Main Types of Australian Opals and Where They Are Found

It is important to distinguish the differences between common opal vs precious opal. Common opal is colorless opal that has formed with a very weak silica sphere structure. This opal is usually referred to as potch. Precious opal on the other hand has a well formed silica sphere structure. These opals have good play of color and are vibrant when exposed to light. Unlike some other gemstones, the most important thing to note about precious opal is that it does require good light exposure so show off at its best. Common opal is often left attached to the precious opal when cutting to give the opal a backing with a strong body tone. You can often judge the body tone of a Lightning Ridge opal by the shade of black/grey potch on the back of the opal.

Potch left on the back of the Black Opal. This one is a deep black which results in a very strong body tone

Australia boasts several distinct types of precious opals, each with unique characteristics and originating from different parts of the country.

3.1 Black Opal: Lightning Ridge, New South Wales

Black opal is considered the most valuable type of opal due to its dark body tone, which provides a striking contrast to its vibrant play of color. Found primarily in Lightning Ridge, New South Wales, black opals often display deep blues, purples, reds, and greens, making them some of the rarest gemstones on earth. Their dark background enhances the brilliance of the colors and makes them highly sought after by collectors and jewelers. Did you know that high quality black opals often only have very thin colour bars?

A gem quality Black Opal from Lightning Ridge

3.2 White Opal: Coober Pedy, South Australia

White opal, also known as light opal, have a milky, pale body tone. While generally less valuable than black opals, they can still exhibit a beautiful play of color. Coober Pedy, located in South Australia, is the world’s largest producer of white opal. The town is synonymous with opal mining, and its residents famously live in underground homes to escape the scorching desert heat. Fun Fact - 85% of the world's opals come from Coober Pedy. White opal discoveries have been plentiful in this region.

A gem White Opal from Coober Pedy

3.3 Boulder Opal: Queensland

Boulder opal is found embedded in ironstone rock in Queensland, particularly in areas like Winton, Quilpie, and Yowah. These opals are characterized by their vibrant colors and natural host rock backing, which adds durability and a distinct earthy appearance. This is why they are a popular choice for everyday wear pendants. Boulder opals often showcase spectacular color patterns and are considered a unique category of their own within the Australian opal family. A unique type of opal is discovered in Sandstone opposed to ironstone within the Boulder mines. This type of opal is known as Crystal Boulder Opal (or Pipe Crystal Opal). The sandstone backing creates brighter, vibrant pastel colors and is popularly used in youth style jewelry today. Other varieties of Boulder Opal include matrix opal, fairy opal and the popular yowah nut.

A unique vein pattern Boulder Opal from Koroit, Queensland

3.4 Crystal Opal: various locations

Crystal opal is a term used for opal that is transparent, allowing light to pass through it. These opals can be found in various Australian regions, including Lightning Ridge and Coober Pedy. Crystal opals are prized for their clarity and the depth of color they exhibit, often displaying a liquid like appearance. Crystal opals are popularly used as a cheaper alternative to black opals, and can look just as good with a closed in backing setting.

Crystal Opals are transparent; meaning light can pass through them

4. Opal Mining

Opal mining in Australia is a mix of tradition and innovation. It’s a labor intensive process that often involves family run operations and small scale miners, many of whom still rely on methods passed down through generations. The processes vary depending on the location that is being mined, as some mining is conducted underground whilst other areas operate with large excavator machinery in open pit operations. The mining process typically includes:

Prospecting: Using geological knowledge, historical data, and trial and error to identify opal rich areas.

Drilling and Blasting: Once a promising site is found, miners drill shafts and sometimes use controlled explosives to break up the rock.

Tunneling: Tunnels are dug by hand or with machinery to extract opal bearing material.

Excavating: Open Pit mining operations that are most popular in Boulder mining use excavators to dig the earth in search of precious opal.

Noodling: This refers to sifting through discarded mining debris in hopes of finding overlooked opals

An excavator used in open cut mining in Winton, Queensland

Safety, environmental concerns, government permissions and land rights with both farmers and the native Aboriginal people are increasingly important aspects of mining operations.

5. Opal Cutting

Opal cutting is an art form in itself. Because each opal is unique in color, pattern, and structure, skilled cutters must assess the rough stone carefully to determine the best way to maximize its beauty and value. There is no one right way to cut an opal as every opal needs to be read like a book as an individual piece. Only experience in cutting will make for better cut opals when finished. The cutting process typically involves:

Evaluation and Planning: Determining the orientation that will best showcase the play of color.

Sawing: Cutting the rough opal into manageable pieces.

Grinding and Shaping: Using diamond wheels to grind the opal into the desired shape while preserving as much material as possible.

Sanding and Polishing: Finishing the surface to a high polish to reveal the full spectrum of color and luster.

An opal being shaped on a diamond wheel

Great care is taken during cutting, as opal can be delicate and prone to cracking. Once you cut an opal it cannot be uncut, so often the process can take a very long time whilst the cutter decides on what to do. The final shape is often dictated by the natural form of the opal, sometimes resulting in unique, freeform cabochons that differ from the standardized cuts used for other gemstones.

6. Opals in Jewellery

Opals have captivated jewelry designers for centuries with their vibrant and unpredictable beauty. Their versatility makes them suitable for a wide range of styles; from traditional and vintage to modern designed pieces. Here are some of the most popular uses of opals in jewelry:

Rings: Black, white and boulder opals are often set in gold or platinum rings, where their colors can be displayed prominently.

Pendants and Necklaces: Opals make stunning centerpieces in pendants, especially when paired with diamonds or other gemstones. Black opals and white opals are often associated with higher end pieces, whilst boulder opals can be a better choice for everyday wearing as their harder ironstone makes them sturdier.

Earrings: Smaller opals or matched pairs can be fashioned into elegant earrings.

Bracelets and Brooches: While less common due to the delicate nature of opal, these items are often reserved for special collections or statement pieces.

Ornaments, Souvenirs, Specimens and Carvings: You can find many such pieces in gift shops in Australia. Often sought after by gemstone collectors.

Australian opals are used in both high end and affordable, everyday wearing jewelry

Australian opals are particularly popular in jewelry, as their unique colors and patterns lend themselves to one of a kind creations. Buyers of opals are often seeking unique pieces that suit their tastes, opposed to your traditional diamond rings and gold necklaces with no real style or character about them.

7. Choosing the Right Opal for you

When selecting an opal; whether for a collection or a piece of jewelry, there are several factors to consider. Understanding these will help you make an informed and rewarding choice:

Play of Color: The most important attribute of an opal is its play of color visible within the stone. Brightness, pattern, and color all affect value. Reds and oranges are rarer and more valuable, while greens and blues are more common but still highly desirable if they are of strong appearance within the opal.

Body Tone: This refers to the underlying color of the opal. Black body tones make the play of color stand out more vividly and generally increase value. Light or white opals are softer in appearance but can still be stunning.

Transparency: Crystal opals, which are transparent, can offer a deeper, more luminous appearance. The opaqueness of an opal doesn’t necessarily decrease value, but it changes how the colors present.

Pattern: No two opals are alike. Patterns like harlequin, pinfire, rolling flash, and broad flash are all prized for their visual effects. Some patterns are rarer and more collectible than others; the most sought after usually being harlequin and flagstone.

Size and Shape: Larger opals are rarer and typically more expensive, especially if the quality remains high throughout the stone. Freeform shapes may offer better use of the natural material however they are not as sought after which may result in lesser value. Oval and teardrop cabochons remain very popular for classic settings, while shapes such as heart shaped carvings have become more popular in recent times.

Origin: The source of the opal can significantly influence its value. Black opals from Lightning Ridge and boulder opals from Queensland are particularly esteemed by collectors and jewelers worldwide. People do put more significance onto opals from a particular region over others.

Treatment: Always inquire if an opal has been treated. Natural solid opals are more valuable than doublets or triplets, which consist of layered materials to mimic the look of a solid opal. It is important to assess the opal for any discrepancies as well such as potch marks in the face, crazing or anything else that may devalue the stone.

Australian opals are one of nature’s most captivating gemstones ever discovered by man. The ancient geology of these stones combined with the artistry of cutting will forever hold significant importance within the jewelry and gemstone industries. Each stone offers a unique story into the beauty of the Australian outback. As no two opals are the same, choosing the right one can be an emotional experience; each gem a story millions of years in the making.