Few gemstones are as instantly recognisable—or as captivating—as opal. With its mesmerising play-of-colour and soft, milky body tone, opal has enchanted jewellery lovers for centuries. Its distinctive shimmer, known as opalescence, is caused by microscopic silica spheres that diffract light, producing flashes of every colour in the spectrum.

What Is Opal?

Unlike crystalline gemstones, opal is an amorphous mineraloid made of hydrated silica. This means it has no crystal structure, making it unique among traditional gemstones. Opal can appear in many forms—from creamy white or pale blue to vivid black—often with striking flecks of colour that shift as the stone moves. This visual phenomenon, called play-of-colour, makes each opal one of a kind.

Gemstone Characteristics

• Hardness: 5.5–6.5 on the Mohs scale
• Toughness: Poor (sensitive to drying, impact, and temperature change)
• Lustre: Vitreous to pearly
• Colour: Milky white to black, with multicolour flashes
• Crystal System: Amorphous (not crystalline)

Common Cutting Styles

Because of its softness and unique colour play, opal is usually cut into cabochons that showcase its surface phenomena. Freeform cuts are also common, especially in artisan or one-of-a-kind pieces. In antique jewellery, opals were often surrounded by seed pearls or diamonds to enhance their iridescence.

Use in Antique and Vintage Jewellery

Opals were especially beloved in the Victorian and Edwardian eras. In the late 19th century, Australian opals became widely available and were set into rings, brooches, and pendants. Their ethereal appearance made them perfect for romantic and sentimental jewellery, and they often featured in mourning pieces. During the Art Nouveau period, their organic shapes and shifting colours aligned beautifully with nature-inspired designs.

Symbolism and Lore

Opals have long been associated with hope, creativity, and transformation. Ancient Romans believed they embodied all the virtues of the other gemstones due to their colour spectrum. In the 19th century, they were mistakenly associated with bad luck, a superstition that has since faded. Today, opal is the birthstone for October and symbolises inspiration and emotional expression.

Is Opal Suitable for Daily Wear?

Opals are among the most delicate gemstones used in jewellery. They are vulnerable to scratching, cracking, or crazing (a network of tiny cracks) if exposed to dryness or sudden temperature changes. For this reason, opal rings—especially antique ones—should be worn with care and stored away from hard gemstones and extreme environments. A cool, padded box is ideal.