Yowah nuts are walnut-sized stone concretions with opal in their centers. A split Yowah nut, "Lagoon," Queensland, Australia. Photo courtesy of liveauctioneers.com and Bonhams.

Article: Opals in the Australian Outback

Credit: Bonhams

Gemstone	Opal Stone
Natural or man made	Natural
Origin	Australia
Origin details	Queensland
Gem State	Tumbled
Color	White
Transparency	Translucent
Photo phenomena	Play of Color