One Yowah nut, bisected One of many opal mining sites in the red continent is called Yowah, and is f
One Yowah nut, bisectedOne of many opal mining sites in the red continent is called Yowah, and is famous for its opal nuts, veins of precious glowing opal within nodules of siliceous ironstone that often form amazing patterns. They vary from 0.5 to 20 cm across, and occur in an iron rich sandstone, near the border with an adjoining mudstone. While both halves of this specimen display a bright and powerful play of colour, showing the most valuable display of the full gamut from red to blue, one has emerged as the less valuable white opal and the other as a stunning dark opal, revealing the full play of colour engendered by the silica spheres forming the structure of the gem to its best extent. The reason for this is probably simple, the darker half is most likely thicker, or has a thicker rind of ironstone, and the greater amount of backing darkens the gem by absorbing light.LozImage credit: Eric Welch/The Smithsonian Institution -- source link
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