October's Birthstone: The Origins of Opals

What is an Opal and Where are they Found?

An opal is a unique and captivating gemstone, renowned for its play of colour and distinctive appearance. Unlike most gemstones, opal is non-crystalline. Instead, it is formed from hydrated silica, typically containing between 5–10% water. This high-water content makes opals more susceptible to damage, particularly if they become dehydrated, which can cause the stone to develop cracks or fractures.

Opals are formed in areas with hydrothermal activity and silica-rich deposits. Australia is the world’s leading source of opals, accouting for around 95% of global production. However, opals are also found in several regions across Europe and America, where different deposits produce different varieties with their own characteristic colours, patterns and play-of-colour.

Opals were introduced to Britain during the 1850s, and their extraordinary colours and individuality have ensured their enduring popularity. Today, fine opal jewellery and exceptional gemstones continue to attract interest at auction, where factors such as colour, pattern, transparency, origin, condition and quality can all influence a piece's desirability and value.

In this guide, we delve into the different types of opal, exploring their individual characteristics and the regions around the world in which they are found.

White Opals

The most abundant form of opal is the white or light opal. These opals are most commonly found in Australia, and range from transparent to semi-opaque, with a characteristic milky or light-coloured body tone. The value of a white opal depends largely on its play-of-colour.

White opals displaying vivid, well-defined flashes and a strong play-of-colour are typically considered more desirable and can command higher prices at auction. Additionally, white opals have long been suited to jewellery, where its luminous appearance can be complemented by diamonds, coloured gemstones and intricate metalwork.

Black Opals

Black opal is considered the rarest and most sought-after variety. Despite its name, black opals are not necessarily black in appearance; the term refers to its darker body tone, which provides a deep background and striking contrast against their vibrant play-of-colour. Black opals can display some of the most spectacular flashes of colour, with vivid hues ranging from electric blue and green to red, orange and violet. The finest examples are associated with Lightning Ridge in New South Wales, Australia, which is recognised as an important source of these rare opals.

Fire Opals

While opal is perhaps best known for its mesmerising play-of-colour, fire opal offers something distinctly different. Typically transparent to translucent, fire opals are prized for their vivid body colours, ranging from luminous yellow and golden orange through to deep, intense red.

The warm hues of fire opal are associated with iron within the gemstone, while exceptional examples may also display flashes of spectral colour. Unlike many other varieties of opal, fire opals are often faceted, allowing their transparency, brilliance and intense body colour to take centre stage.

Fire opals are typically found in Mexico, and has a fascinating history rooted in Aztec beliefs. The Aztecs are said to have likened its vibrant colouring to the feathers of hummingbirds, giving rise to the evocative description of it as the ‘hummingbird stone’. Following the Spanish conquest of Mexico in the 16th century, fire opals were introduced to Europe, where their distinctive colour and rarity attracted further attention.

Our Silver & Jewellery auctions regularly feature a strong selection of opal jewellery, attracting dedicated buyers and collectors who value the opportunity to view these distinctive gemstones in person. If you are considering selling opal jewellery at auction, our specialist team would be delighted to offer guidance on your piece and discuss the consigning process. Get in touch with us to find out more about valuing your opal jewellery for auction.