Opal Types

Blacks, Whites, Crystals, Boulders, Pictures...

On this page, you can discover the different types of opals found in Australia, including the well-known black opals.

Opal types

Precious black opal consists of a layer of colourful precious opal on black potch opal.

Precious dark opal consists of a layer of colourful precious opal on dark grey potch opal.

White opals have a lovely white or very light body tone.

Crystal opals are transparent opals with colour an and/or in the stone.

In picture opals the colourful opal is mixed with potch, forming pictures and patterns.

In boulder opals the colourful opal has formed with ironstone.

Precious Black Opals

Black opals are named after their dark base color, which is black or very dark grey. However, a black opal that is solely black is of no value. Precious black opals consist of a layer of opal that has play-of-color on a very dark grey to black potch opal. The gemstone is still entirely opal and has formed naturally as a single solid piece. The dark base enhances the colors on the black opal, making them glow and stand out.

Black opals are generally the most valuable of all opals and are almost exclusively found in Lightning Ridge, Australia. Some limited production also comes from Coober Pedy, Mintabie and Allan’s Rise in South Australia. The prices of black opals vary greatly, ranging from approximately 100 euros to tens of thousands of euros per carat.

To grade black opals, a body tone scale has been developed. Only opals with a body tone of N1 to N4 can be called black opals. The body tone is determined by holding the stone face up on the scale and comparing its overall body tone to the shades on the scale.

It should be noted, however, that body tone is only one factor that influences the value of a black opal. The body tone scale only applies to black and dark opals and should not be used to grade white opals. Being on the other end of the scale does not mean that white opal is of lower quality than black opal.

Body tone N1 black opal
Extremely rare harlequin pattern black opal
A ring with a black opal
Opaalikoru, Tiffany, 1929
L.C. Tiffany opal necklace from 1929. Large black opal from Lightning Ridge set in yellow gold.

Dark opals, sometimes called as semi-black opals, are formed in the same way than black opals, with a layer of precious opal over grey colourless potch opal. The body tone of dark opals is either N5 or N6 on the body tone scale.

Often dark opals are more affordable than black opals. However, the body tone is only one factor affecting the pricing of a stone and the over all aesthetics and quality of the stone is what determines the price.

Tumma opaali Lightning Ridgestä
Gem grade dark opal with N6 body tone

White Opals

The best white opals are mainly found in the Coober Pedy mining area in Southern Australia. The colors, patterns, and play of colors on a white opal can be just as stunning as on black and dark opals.

On white and light opals, the color can be over a light base opal as well as on black and dark opals. Alternatively, the stone can entirely comprise white opal that is full of color, often called white crystal opal.

The sophisticated and elegant beauty of white opals suits Scandinavian and European tastes. White opals are often larger than black opals, hence offering more options for necklaces, pendants, and bracelets. Large white opals are also significantly more affordable than black opals in the same size range.

Coober Pedy White Crystal Opal
White crystal opal - Coober Pedy Australia
Coober Pedy jalokivi opaaliraakakiveä
Rough white opal from Coober Pedy, Cranbrook Institute of Science, Michigan, USA
Valkoisia opalisoituneita simpukkafossiileita Coober Pedysta
Opalized Cyrenopsis fossil bivalves from Coober Pedy
Koru valkoisilla opaaleilla ja siperian ametisteilla
René Jules Lalique Necklace, c. 1895-1905, gold, enamel, Australian opal, Siberian amethysts

Crystal Opals

Crystal opals are unique among black, dark and white opals as they are transparent. They can either be completely transparent or opaque with or without a body tone, which can range from white to black. Black crystal opals are extremely rare and highly coveted.

Crystal opals are one of our favourite types of opals due to their versatility. The colours in crystal opals can appear on top of the stone or be embedded deep within it, creating a layered and vivid colour play. The play of colours in crystal opals is often lively and attractive, but it can be difficult to capture in static photographs. That’s why we always provide a video of each stone in our shop to ensure that it’s presented as accurately and vividly as possible.

Crystal opals can sometimes be cut to be double-sided, which allows them to be set in various ways, including open settings where the stone is visible from both sides.

The setting and background of a crystal opal can have a significant impact on the appearance of the stone. Therefore, it’s essential to take special care when selecting settings for crystal opals. They often appear lighter in person than in pictures, and skin is often a great background for them. If the stone has sand or other inclusions on the background, it’s advisable to set it on a solid, non-transparent background.

Picture Opals

In picture opals, the colourful precious opal is mixed with the colourless potch opal, forming pictures and patterns. Picture opals can be very attractive and interesting stones that leave room for imagination.

Picture opals are usually significantly lower priced than the other solid opals as the colourful precious opal doesn’t cover the whole stone. On the other hand, it makes these stones especially interesting.

Boulder Opals

Boulder opalGeological Origin and Formation

Boulder opal, a distinctive gemstone primarily sourced from Queensland, Australia, is formed within ironstone boulders through sedimentary deposition and ionization processes. These ironstone concretions are solid masses that vary in hardness and are mainly composed of iron oxides, silica and a small amount (about 1%) of water. The shapes of boulder opals can range from elongated to ellipsoidal, with sizes varying from a few centimetres to impressive diameters of up to 3 meters. Their placement can be either within specific layers or distributed randomly across weathered sandstone, highlighting the gemstone’s diverse natural formation environments.


Types and Characteristics of Boulder Opal

Opal in boulder opals manifests in various ways, either as a filling between ironstone layers, within cracks or as a core in smaller concretions known as “nuts.” This diversity in their formation contributes to the unique appearance and colour patterns of each stone. Boulder opals are renowned for displaying a wide spectrum of colours that include vibrant blues, greens, reds, and yellows. The ironstone matrix in which the opal is embedded often enhances these colours, providing a dark backdrop that makes the opal’s hues appear more vivid and intense. Types of boulder opal include:

  • Matrix Opal: Features a mesmerizing network of opal veins within the host rock, creating intricate patterns.
  • Seam or Band Opal: This form presents linear patterns encased within ironstone layers, prized for its unique aesthetic.
  • Pipe Opal: Identified by its tubular formations within the sandstone, these structures can be both hollow and opal-filled.
  • Wood Opal: Formed when opal replaces organic material, retaining the original textures and patterns of the wood.


Cutting Boulder Opal

The integration of boulder opal with its ironstone matrix distinguishes it from other opals. When cut for jewelry or collections, the natural ironstone backing is often retained, accentuating the opal’s natural colors and providing a stark contrast that highlights the gemstone’s beauty. In instances where the opal layer is sufficiently thick, solid opals may be cut from the ironstone, offering an alternative aesthetic appeal.

Latest Opals in Our Shop