Back to gem encyclopedia

Opal

Fireworks. Jellyfish. Galaxies. Lightning. Opal’s shifting play of kaleidoscopic colours is unlike any other gem.

Responsive image
Cabochon

Most opals are cut as cabochons; this one from Ethiopia weighs 20.86 ct.

Responsive image
Unique Beauty

The play-of-colour displays the entire spectrum over a light grey background.

Responsive image
Pattern

Bright flashes of colour skip across this stone’s surface.

Responsive image
Responsive image
Hidden Beauty

Opal forms as irregular nodules or seams in volcanic or sedimentary rocks.

Responsive image
Rare Phenomena

Play-of-colour results when light interacts with orderly stacks of spheres.

Responsive image
Treasure

This opal nodule displays the promise of intense play-of-colour.

Responsive image
Tools

Buyer's Guide

Individual opals can vary widely in appearance and quality. As diverse as snowflakes or fingerprints, each gem can differ noticeably.

FIND A JEWELLER

Submit your gemstone through your local jeweller. 

FIND A REPORT

Verify the information on your report matches what is archived in the GIA report database.

What to look for

Black opal
Play-of-Colour Is The Most Important Quality Factor For Opal.

There are three main aspects of an opal’s quality. Colour refers to background colour and play-of-colour. Pattern is arrangement of play-of-colour. Clarity means transparency and quantity of inclusions. Play-of-colour might be the most spectacular aspect of an opal’s appearance.

Crystal opal
Clarity refers to the gem’s inclusions.

With an opal, clarity is its degree of transparency and freedom from inclusions. An opal’s clarity can range all the way from completely transparent to opaque. Experts prize different levels of clarity for different opal types.

Freeform shape black opal
Cut Is One Of The Most Important Factors In Appearance.

The cutter considers an opal’s colour, pattern, and clarity when planning the finished gem. As with many top-quality coloured stones, exceptional opals might not be cut to standard sizes and shapes. Domed surfaces give the best play-of-colour.

117.85 Carat Australian light opal cabochon
Carat weight allows for precise measurements.

Common sizes for many of the opal cabochons set in jewellery are 6×4, 7×5, and 8×6 mm. Opal however comes in a wide range of sizes.

Opal Quality Factors: The Comprehensive Guide

Tips & Advice

1. Find a jeweller who carries a wide variety of opal.

Commercial-quality white opal is affordable and available in almost any jewellery store. But before you decide what kind of opal you’d like to own, be sure to see some high quality unusual opals with dramatic play-of-colour too.

2. Consider a doublet or triplet.

If you prefer the look of black opal or boulder opal but it doesn’t fit your budget, you also have the option of an opal doublet or triplet.

3. Don’t expose an opal to extreme light, heat, or dryness.

Opal has high water content. Although most opal is cured to make sure it won’t crack, it’s never a good idea to subject your opal to very dry or hot conditions.

4. The best pattern is the one you like best.

Buying fine opal is a bit like buying art. Every pattern of play-of-colour is different; some bold, others delicate, some symmetrical, others dynamic. There is no wrong or right, so choose what appeals to you.