The rough specimen is a thin seam of boulder opal on sandstone host rock. The 3.47-carat boulder opal tablet was cut from a similar piece of rough.
This black opal exhibits exceptional play-of-color. - Courtesy Cody Opal
With proper care, opal jewelry will provide years of enjoyment. - Courtesy Cody Opal
Figure 3. Raman spectra of untreated, oil-treated, and Opticon-treated opal. The oil-treated opal shows characteristic Raman peaks at 2929, 2897, 2873, 2851, and 2724 cm–1. The Opticon-treated opal displays characteristic Raman peaks at 3071, 2931, and 2873 cm–1, with a series of smaller peaks in the 600–1600 cm–1 range.
Figure 2. FTIR spectra of untreated, oil-treated, and Opticon-treated opal. The two treated opals show characteristic FTIR peaks in the 5600–5900 cm–1 range, while untreated opal does not show any peaks in this range.
Figure 1. Top: These five opal slices of comparable thickness were cut from the same rough. They were semitransparent to translucent when viewed in daylight on a black background. Play-of-color was displayed with oblique lighting at certain angles. Bottom: The slices’ transparency improved after immersion in distilled water for approximately 20–30 minutes. Each slice absorbed water differently depending on its porosity. Photos by Nuttapol Kitdee.
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