Oval-cut white opal gemstone

This item appears to be a loose, polished opal gemstone with an oval cabochon cut. The stone exhibits a milky white to translucent base body color, which is consistent with the characteristics of white or light opal. Across the surface, a 'pinfire' or 'mosaiced' play-of-color is visible, displaying vibrant flashes of green, orange, yellow, and subtle pinkish-red under the light. The shape is a symmetrical oval with a smooth, domed top (cabochon), and the surface appears to be well-polished with no immediate cracks or significant surface chips visible, though microscopic abrasions may exist. The user-supplied information identifies this as an 'Opal Coober Pedy 11 cts'; however, these claims of geographic origin and specific carat weight are unverified without a physical gemological lab report and precision weighing. The appearance is stylistically consistent with material found in South Australian mines, such as Coober Pedy, but such a determination cannot be made with certainty from a photograph alone. The stone's quality is indicated by the brightness of the color flashes and the evenness of the cabochon shape. In-person testing for density, refractive index, and inspection for natural potential inclusions would be necessary to determine if the stone is a natural solid opal, a doublet, or a triplet.

I have examined the images of this loose gemstone, which appears to be an oval cabochon white opal. Per the user's submission, this is an 11-carat opal from Coober Pedy. Based on what I can see, the stone exhibits a desirable 'pinfire' play-of-color with visible green and orange flashes across a milky white base. I cannot verify the exact carat weight, geographical origin, or whether this is a natural solid stone from a photograph; physical testing for refractive index and specific gravity would be necessary to rule out a doublet or triplet construction. The estimated value of $650 - $1,100 assumes the hypothesis that the stone is a natural, solid opal of the stated weight and origin. This range is based on typical market demand for white opals with moderate-to-high brightness. If the stone is found to be a doublet or triplet (an assembled composite), the value would likely drop significantly to under $100. Conversely, if it is a natural solid but features a different origin than Coober Pedy, the value might fluctuate based on the specific body tone and brilliance. To establish a more precise valuation, a gemological laboratory report is required to confirm the stone's solid nature and specific measurements. The current market for Australian white opal remains stable, though stones with diverse color play and high clarity command the highest premiums.