GRADING REPORT OPOB288
- Identification: Natural Unheated & Untreated Black Opal
- Carat: 2.88
- Shape: One-sided Flat Cabochon
- Measures: 9.25x7.71x6.34 (millimeter)
- Body Color: Blue & Yellow/Brown
- Play of Color: Good
- Pattern: Wide Flame
- Clarity: Translucent
- Cutting Grade: Very Good
- Finish: Very Good
- Depth: 82%
- Origin: Lightning Ridge, Australia
Treatment: None
Certificate No: IGI 296721366
Overall Grade: Good
Comment: Lastly, for this month, we come to the oldest classic from the, equally classic and famous, Lightning Ridge in NSW, Australia. A black opal with dark blue-violet play-of-color. Like others from famous mines, like Mogok, the most perfect pieces are exceptionally expensive, and not for beginners. This 2.88 is of solid weight, in fact the heaviest gem so far, but not the biggest in dimensions at all. Like dark blue sapphire, it depends much on the light conditions. Under bright day-light it plays with most beautiful violet-blue shades in Medium Dark 70 to 80, comparable to fine kashmir-blue sapphire. Less light, however, gives rise to shadows and midnight blue areas, and also deep black valleys. Nothing boring there, but not the most expensive play-of-color. In perfect variations this type of opal is often called 'investment opal' and the price-tag will ask for one or two digits extra. See the back-side and side-view images and marvel at the build-up and inner structure, inside a transparent yellowish body, with a layer of dark blue clouds upside and an earthy plane of dark brown-black on the bottom. Without much imagination one can compare this to a cut-out of earth's atmosphere at late dusk. Dark blue sky above, (somewhat polluted) air inbetween and a flat plateau of solid rock below. Perhaps the closest we come to compare with other facetted gems, a kashmir blue sapphire in cabochon cut. No treatment, no visible inclusions only wafting blue clouds, perfect cut and polish. Ideal for a deep-set, heavy bezel-ring. Other than the crystal- and fire opals, this type does loose hue and tone with low light, hence study the image in low light, dark, yes, but even there we find no complete black-out; the deepest of all possible blues survives to meet the eye.
