A rich seam of wonderfully irridescent opal, flashing gold and blue fire, encased in matrix! This is a very large and striking opal specimen. The layer of precious opal is a good 0.5 cm thick, and under it is a thick layer of common opal. Its from the central Queensland opalfield, perhaps the Quilpie or Yowah area. How do we know? Thanks to a friend over there who provided the following details: The matrix is an brown iron-stone or jasper-like rock, which is characteristic of the Queensland stuff. Coober Pedy opal is always hosted in white to greyish clay rich sandstone (usually quite fragile), kaolin or very rarely pale white/grey cherts. You just do not get those brown jasperoid nodules in Coober Pedy. In the Yowah area of Queenland that they are called Yowah Nuts and they are more like a septarian nodule with the cracks filled with precious opal. Also the opal has a characteristic blue background which you do not really get at Coober Pedy. 11.0 x 7.2 x 4.8cm