How Opals Are Formed

Opals are created over very long periods of time through the cycle of water picking up silica and depositing it into voids and cracks in the earth, eventually forming opal.

Think of the inside of an opal as a bag of marbles.  This gives you an understanding  how the silica spheres are arranged within the opal. It’s interesting to know that smaller spheres are more common and tend to diffract colors like purple, blue, and green, while larger spheres are rarer and showcase the colors of yellow, orange, pink, and red. This helps explain why these colors are less common and highly valued in Australian Opal.

Overall, the process of how opal is formed and the way its silica spheres are arranged within the gemstone are important factors that contribute to its unique properties and desirability.

Geological history shows that Australia was embedded in the ancient southern super-continent of Gondwana.  An inland sea covered central Australia.  Silicia filled the cracks in rocks and layers of clay.  Some of those deposits became precious opals.  

It takes 5 – 6 million years to make a 1 cm opal to mature.