This is a natural piece of boulder opal, showing a literal "stream" of opal running through classic matrix. When you talk about opal in its natural rock setting, you almost always are referring to the classic look of these pieces. However, most are jumbly nodules and lack the interesting, pattern-like aesthetics of the opal as it flows in this specimen. Buffed, obviously, to show the opal to advantage, this specimen has a good balance of color in the rock and shows how the stuff forms in nature. Weighs 286 grams.