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Opal
Chip Clark
Specimen | Catalog Number | Locality | Weight |
---|---|---|---|
Opal | NMNH G9266 | Australia, South Australia | 174.86 ct |
World-famous Australian opal (below) formed when silica-rich groundwater trickled down through sediments until stopped by a layer of clay. As water evaporated from the trapped solution, the silica formed microscopic spheres that settled into an orderly arrangement.