One of the beauties of the world of gemmology is the sheer diversity of the gems that nature produces. But let's be honest: few have the same lore, impact and history as Opal. This gem, although semi-precious, commands some of the highest prices per carat. In this guide, our goal is to look into the world of opal, and explore its properties, history and most important of all, symbolism.
What is Opal?
Opal is a semi-precious gem that has a significant water content in its structure. More precisely, it has a chemical structure SiO2.nH2O and is a mineraloid. A mineraloid is a mineral that has no formal atomic structure; unlike the majority of other minerals found in nature. It is primarily composed of hydrated silica, a form of silicon dioxide but with additional water in its structure. The remaining 10 or so percent of opal is water.
How is Opal formed?
The majority of opals are formed in Australia, with a significant percentage also coming from Ethiopia and Mexico. Opals are formed in different way, and each of these three nations have different formation methods for opal. Australia, being the most important global supplier of opal tends to be the one we discuss the most in the jewelry trade.
As water hits the ground, it travels downwards through the earth and combines with silica. This silica and water solution enters the cracks and voids under the surface, creating silica deposits over millions of years as the water evaporates during summer. The stone we know as opal is formed.
Cracks in the ground, such as the one above is where silica deposits form opals over millions of years.
What types of Opals are out there?
Although a diverse family of gems, opals can be divided into two main categories: Common and Precious Opals. The play of colours within the gem is what determines its classification and therefore its value.
This necklace showcases the exquisite play-of-colour visible in precious Opals.
What do we mean by play-of-colour?
Take any shiny opal and you'll see different colours and lights reflect back. This reflection of endless colours is known as 'play-of-colour' and can be found primarily in Australian and Ethiopian Welo opals. As light enter the surface of the opal, it is reflected in all directions by the internal structure of the gem.
WHAT COLOUR RANGES DOES OPAL HAVE?
WHAT IS OPAL'S SYMBOLISM?
Healing stone thought to once cute eye disease;
Brought to be a stone that brings good fortune, especially wealth;
Used in some cultures to help with preventing one from suffering from the evil-eye.