💎 Understanding Australian Opals: History, Formation & Trade

Opal Options
Mar 26, 2025
3 min read

🕒 Reading time: 4 minutes

In this article, we’ll explore the rich history of Australian opals, delve into the unique geological process behind their formation, and uncover the origins of the opal trade in Australia.

Did you know? Australia produces over 95% of the world’s opals. With their one-of-a-kind color play and natural origins, Australian opals are considered the most desirable globally - and only a few countries in the world host major opal deposits.

🌏 A Brief History of Australian Opals

Over 140 million years ago, an inland sea rich in silica sands covered a large part of what is now central Australia. As this ancient sea slowly receded, it left behind one of the most important geological regions in the country: the Great Artesian Basin.

This massive underground water system played a key role in what would become the formation of opals across Australia’s dry interior.

💧 How Australian Opals Are Formed

Fast forward to 30–40 million years ago, Australia’s climate began to shift, softening the silica within the rock layers of the Great Artesian Basin. Over time, tiny cracks and voids in the rock began to fill with silica-rich water.

Through natural pressure and evaporation, the silica hardened into microscopic spheres - forming the incredible play-of-color we now associate with Australian opals.

🧪 What Is Silicate?

Silicates are the most abundant class of minerals on Earth - and the building blocks of opal. Silica (SiO₂), a type of silicate, is dissolved in groundwater and later deposited into rock cavities, where it forms opals over millions of years.

Silicates make up approximately 90% of the Earth’s crust, and are essential to the structure and sparkle of the Australian opal.

📍 Where Are Australian Opals Found?

While the Great Artesian Basin spans a vast area across eastern inland Australia, true opal-producing regions are few and far between. Even in historically rich fields like Winton, Quilpie, and Yowah, finding high-quality opal is a rare and rewarding event.

That’s why Australian opal is considered so valuable - each piece is the result of a unique natural process, millions of years in the making.

🛍️ The History of Opal Trading in Australia

My Great Grandfather's mine - 1902 Hausington Mine

The modern era of opal mining began around 1889, but it wasn’t until a man named Tullie Cornthwaite Wollaston brought rough opal from Queensland to London that Australian opal began to gain global recognition.

Wollaston successfully sold his opals to a prominent European , and from that moment, the demand for Australian opal exploded. Since then, opal has become a coveted gemstone among jewelers, collectors, and lapidary artists worldwide.

🌍 Today’s Australian Opal Market

Today, Australian opal is internationally recognized as the world’s premium opal source. Many lapidary clubs, jewelry designers, and gemstone collectors rely on Australian-sourced opals - particularly boulder opal, white opal, and crystal opal - for their richness, quality, and unique natural character.