Precious Opal in Matrix

Hardness: 5.5-6.5 on Mohs scale; Color: Multi-colored play-of-color (iridescence) within a tan to brown host rock; Luster: Vitreous to waxy; Crystal Structure: Amorphous (non-crystalline); Specific Gravity: 1.9-2.3.

Formed from silica-rich water seeping into cracks and cavities in sedimentary or volcanic rock. Over millions of years, the water evaporates, leaving behind silica spheres. The play-of-color occurs due to the diffraction of light through these ordered spheres. Often associated with the Cretaceous period in Australian deposits.

Primarily used as a gemstone in jewelry (rings, pendants) and highly valued by mineral collectors for its unique optical properties.

Australia produces about 95% of the world's precious opal. The specific location provided (near Perth, WA) is more known for its proximity to the Darling Scarp, but Western Australia does have minor opal occurrences (like Coolgardie), though most commercial precious opal comes from the Great Artesian Basin in SA, NSW, and QLD.

Identify by the characteristic 'play-of-color' or 'fire' flashing when rotated under light. Look for layers or veins of glassy material embedded within a duller sandstone or ironstone matrix.