Complete Opal Guide
Opals are a beautiful stone that offer a variety of unique colours. Our guide will give you some more information around the different types of opals, where they come from and how to choose which one is best for you.
Opal in general:
90% of opals are found in Australia, with the other 10% spread across the world from Mexico to the USA and the Czech republic. They come in various tones and colours. Opals are found in pockets in rock like sandstone, limonite and basalt. It is thought they are formed by water seeping through and evaporating, leaving behind traces of minerals like silica that create the various coloured opals.
Opal comes in a wide variety of colours and types based on the changes in mineral content.
The different types may be made up of a single colour or represent all the colours of the rainbow. Each stone tends to have a dominant background colour creating five main types:
Considered the rarest but most beautiful stones, black opals have a dark background creating a strong contrast to the rainbow colours that shine across the surface.
Boulder opals tend to have a similar appearance to black opals. The main difference is their dark background colour is caused by the underlying rock from which they were mined. When cut the host stone is kept as an integral part of the stone to give a more vibrant overall appearance.
Fire opals tend to have a yellow, orange or red background hence their name. They are commonly found in Mexico.
Varying from opaque to translucent, white opals have light coloured backgrounds. They can vary in colour from white to lighter tones of blue and pink and can display plays of colour over the top giving a more traditional rainbow look.
Crystal opals can vary from semi to fully transparent in their background colour. This does not hinder them however as they can have one of the brightest displays of colour overall.
Check out the beautiful Opal ring pictured above here
Opals like diamonds can come in various cuts, sizes and weights whilst also having different colours and clarities. However, unlike diamonds, opals also have factors like patterns and colour plays.
Cut and Weight:
As opals are formed in pockets within rocks they often are not cut into conventional shapes due to the cutter wanting to preserve as much weight and colour as possible. This is especially true with rarer diamonds like a black opal, as they are much more valuable. Opals may be cut into slices and combined with a backing like glass to utilise as much of the stone as possible. This massively reduces the overall value of the stone creating a more affordable option.
When deciding on a cut, affordability is a key factor alongside personal preference.
Colour, Pattern and Clarity:
Opals, unlike other stones, are prized for their ability to show various colour and patterns. They often show different colours depending on the angle and light. The more angles the colours are visible from the more valuable the stone. In general larger batches of colour that are close together are more prized than small batches further apart. Opals can also be devalued by having large spots without colour alongside internal cracks and contaminants like dirt. Diamond transparency is not as large a factor on the value of the opal unless it is dulling the effects of the colour changes on the surface of the opal.
Overall when choosing your opal the main factor comes down to personal taste. Having a stone with the shape you find most pleasing alongside the colours and pattern you enjoy, you will be investing in a one of a kind piece that can be passed on for generations. Unlike diamonds, opals are a limited resource so choosing a piece with the colour and pattern you enjoy is a solid investment for the years to come.
For further information about opal quality, check out the leading jewellery gemstone association the GIA’s article on Opal Quality factors: https://www.gia.edu/opal-quality-factor