Finding an Opal Field
In Australia, most opal occurs in clay layers underneath sandstone. However, in other parts of the world, opal is associated with volcanic rock. The silica-rich geothermal fluids that flow in volcanic areas can often produce opal. In Ethiopia and Nevada, opals occur at the transition between layers of sediment and volcanic rock. In contrast, opal from Mexico and Oregon forms in gas bubbles in ancient lava flows.
Although opal occurs frequently in volcanic areas, finding opal with precious play of color takes some luck.
Opal Prospecting Methods
Once you find an opal field, you need to know where to open a mine. Typically, this means digging a hole to the opal-bearing strata and searching for the gem in this layer. If there’s no opal, you can move on to the next hole without too much cost. However, new geophysical techniques can show you exactly where to dig (but will cost more initially).
In this video, Sebastian shares his experiences prospecting for opals in Lightning Ridge, Australia. Video © Black Opal Direct. Used …