Boulder Opal Jewelry
Precious opal formed in veins of ironstone and cut with its host rock attached. From Queensland, Australia
Unearthed Gemstones Boulder Opal Jewelry
Click the photos for a closer look of the jewelry pieces
Hardness
5.5 - 6.5 (Medium): Wear with care; This gemstone can dull over time.
Toughness
Fair (Needs care — Vulnerable to knocks and sharp blows)
Mineral Family
Opal
Transparency
Translucent to Opaque
Crystal System
Amorphous
Lustre
Vitreous
What Is Boulder Opal?
Boulder opal is precious opal that formed in thin veins and pockets inside ironstone boulders. Cutters leave the opal attached to its host rock, so each stone is a slice of gem and earthy brown ironstone together. That dark natural backing makes the play-of-colour glow vividly, a bit like a built-in black opal effect. It comes almost entirely from western Queensland in Australia, from opal fields around Winton and Quilpie. Every piece is cut freeform to follow the vein, so no two are alike.
Is Boulder Opal Durable Enough for Everyday Jewelry?
The opal layer sits around 5.5 to 6.5 on the Mohs scale, but the ironstone backing gives boulder opal more stability than most solid opals. It is cut as cabochons and freeform shapes for pendants, earrings and occasional-wear rings. Because the dark backing is natural rock, boulder opal gives you doublet-style drama in a fully natural, untreated stone.
How to Care for Boulder Opal Jewelry
Treat it kindly: no ultrasonic cleaners, no harsh chemicals, and avoid sudden heat. Just wipe it clean with a soft, damp cloth.
Gemstones Similar to Boulder Opal
Other varieties in the opal family.
