Fossicking
My father and I just got back from a trip to Lightning Ridge to look for opals. We had a great time and we were much more successful than we have been, panning for little specks of gold. Mud collects on the bottom of the ocean, and gets compacted into rock. Then then rock cracks and water fills on those fissures. Over time silica is deposited in those fissures. The silica is commonly a greyish blue colour (potch), but sometimes comes out sparkly. This is what we call opal. Over time, through geologic processes, the mudstone is carried upward, above sea level. In Lightning Ridge they bore tunnels into the mud stone looking for opals, and the gravel they dig out is just left on the side of the road. In fact, the roads are lined with this gravel. When it rains the mudstone is washed away, leaving behind the potch and little fragments of opal that the miners missed when they dug up the gravel. Fossickers walk along the side of the road looking for the sparkly stuff. I collected ...