Boulder Opal Rough Appraisal

Rough Queensland Boulder Opal Specimen

This specimen is a rough, unpolished Boulder Opal, characteristic of the mining regions in Queensland, Australia. The item consists of a dense, dark brown ironstone host rock matrix measuring approximately 4-6 centimeters in length. A distinct, thin undulating vein of precious opal is visible running horizontally through the ironstone. The play-of-color within this vein displays vibrant electric blue and cyan hues, which contrast sharply against the earthy, chocolate-brown tones of the matrix. The physical structure of the piece shows a raw, uneven surface with a botryoidal or 'bumpy' texture along the top ridge, exhibiting a mustard-yellow to ochre-colored clay or sandstone coating. The primary ironstone body shows natural sedimentary banding and a matte finish, indicating it is in its natural state post-extraction without significant lapidary work. Notable features include the high saturation of the blue 'fire' in the narrow opal seam, which suggests high-quality silica spheres within the vein. There is no evidence of fractures or 'crazing' (fine surface cracks) within the opal seam, which is a positive indicator of stability. This specimen represents a natural mineral formation that is millions of years old, typically harvested from Cretaceous period deposits. Its value is derived from the brightness of the color flash and the integrity of the ironstone host.