RV prospectors who frequently camp on any of the millions of acres of public lands administered by the U.S. Department of the Interior, Bureau of Land Management, or Department of Agriculture U.S. Forest Service may find themselves in remote country with a good chance of discovering a geological anomaly: an ancient streambed.
If you are hiking around looking for a good place to prospect, you will no doubt stay close to active streams, as the banks and bars of these are excellent places to find gold. However, there is another place you might want to prioritize.
How to spot an ancient streambed
Walking around in the forest or even on ridges or plateaus, you may happen upon ground characterized by smooth rocks and gravels—their sharp edges polished. You’ve stumbled upon an ancient streambed.
Such ground may be pretty close to existing drainage, i.e., creek or river. Or it may be a considerable distance and at a higher elevation than any watercourse nearby. Nevertheless, you can be sure that at some point in the area’s history, an ancient stream ran here, carrying the materials of erosion of rocks and mineral deposits from way back in geologic time. Here is a location where you will want to do some digging.
Your ancient streambed may have coursed near a current stream, but likely at a higher elevation, creating a “ledge” or large gravel deposit. Of course, it’s possible and not uncommon to find such gravel deposits at some distance from the existing drainage. If the ancient gravels are close enough, you can carry the gravel down to the running water and then pan them out or run the material through your sluice box. If, on the other hand, your prospect is at a distance, or you are otherwise prevented from reaching the current stream, you will have to decide whether to use a “high banker” or some form of dry sluice or rocker box. It will probably be desirable for the typical RV prospector to process the material with the least amount of sophisticated, costly, mechanical equipment.
What’s so important about an ancient streambed?
A prospector discovering an ancient streambed has made an important find for several reasons.
First, it represents ground where mineral deposits were washed downstream through hydraulic erosion in ancient geologic times. Such gravels are often among the richest placer deposits a prospector can find.
Second, though it seems unlikely in the modern day, it is nonetheless quite possible that your ancient streambed prospect may have escaped notice or discovery by previous prospectors and is thereby wholly virgin, undisturbed riverbed—a potentially rich source of placer gold!
If you find a historic streambed, try to dig your initial prospect hole at the place where the old gravels contact bedrock. Most likely, this is where the placer gold has come to rest. However, there are no absolutes—like every other aspect of prospecting. You may find free native gold scattered throughout the strata of the gravel layers, particularly if you are working in clay-type river bottom soils.
Good luck and happy prospecting!