5.50 Ct. Cabochon Boulder Opal from Australia

This piece is a 5.50 carat Australian Boulder Opal, presented in a fancy shape, with precise dimensions of 23.50 x 8.90 x 3.73 mm, and executed as a cabochon cut to optimize play of color. The cabochon profile is a low to moderate dome, shaped to preserve the natural ironstone backing typical of boulder opal specimens, which provides structural stability and contrast to the opal seam. Optical properties are described as translucent with intense color intensity, the transverse light interaction producing vivid red, blue, green and violet flashes that shift with viewing angle. The color pattern ranges from fine pinfire at the thinner edge to broader flash areas across the central table, indicating variable silica thickness and tightness of the silica spheres. The lapidary work shows careful preforming to follow the natural seam, controlled removal of matrix to reveal the color bar, and a final polishing stage that yields an excellent polish across the domed surface while maintaining the integrity of the host rock on the pavilion.

From a technical standpoint this specimen is unenhanced, no treatments or impregnations, and is therefore in its natural state as mined in Australia. The dimensions and thin profile suggest that the cutter prioritized maximum color exposure while retaining a robust ironstone backing, a typical approach for high quality boulder opal to prevent cracking and to enhance durability in jewelry settings. For setting considerations the elongated, asymmetric fancy shape and shallow depth recommend a bezel or inlay setting to support the perimeter and protect the thin edges, while allowing the face up color to dominate. The combination of intense color play, translucency, and excellent polish makes this stone particularly suitable for signature pendants or bespoke rings where orientation and light exposure can be optimized. The Natural Gemstone Company presents this Boulder Opal with full disclosure of origin, cut, and enhancement status, and the provided measurements and weight allow precise planning for mounting and appraisal, for clients who require technical fidelity and craft focused descriptions in their selection process.