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Yowah Opal Nut

Freeform-cut opal weighing 29.83 ct.
Photo by Ken Larsen. Click to zoom.
Catalog Number NMNH G10650-00
Locality Queensland, Australia
Weight 29.83 ct

Gift of Richard Ashley Foundation in 2010.

The Yowah opal field is a small mining area in the southern part of the boulder opal producing region in Queensland Australia. A famous opal dealer, Bryan Rossiter, discovered this remarkable field and became the manager of the Southern Cross Mine, the first mine to be registered in Yowah on Sept. 1, 1884. Opal mining in the area was very difficult. With little vegetation and extreme drought, obtaining water and food was difficult. The Southern Cross Mine was the home of the famous “Yowah Nut,” precious opal found in ironstone nodules or concretions. These “nuts” can reach sizes up to 20cm across. They have a spherical or ellipsoidal shape and show alternate concentric rings of light and dark brown siliceous ironstone. The miners split the Yowah nuts in half by cracking or sawing to find the gem opal deposits in the center. This Yowah nut exhibits an outstanding example of gem quality precious opal. The play-of-color is spectacular, with flashes of red, orange, yellow, green, blue and purple. The fact that opal in one half of the concretion has a white body color and the other blue, makes this specimen all the more unusual. This is probably due to the thickness of the opal and the dark layer of manganese oxide between the opal and the ironstone causing the thin half of the nut to have a dark body color.  Rod Griffin, the miner who discovered this opal nut, believes it is the finest he has unearthed to date. This rare specimen is an important and beautiful addition to the National Gem Collection.



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