Reading a Stream (Part 3)
Here is some additional information on reading a streams and the sorts of signs and portents that may make your day out there.
Gold Travels Downward
First and foremost, remember that gold is an extremely dense and heavy metal with a very high specific gravity. What does this mean to you? It means that gold in a streambed will eventually work its way down through layers of gravel and rock until it can travel no deeper. That's why finding and working bedrock (or sometimes "false" bedrocks such as caliche or clay layers) in a stream should be your first priority. Sure, you can still find flour gold, flakes, and even small nuggets mixed at various levels above bedrock, but this gold is in transition to lower levels and rarely provides opportunities for uncovering gold pockets or paystreaks of size and substance.
You would do well here to remember that in a streambed with a regular flow of water the physics of gold deposition (something you should study and learn well) remain constant. However, in drywashes and arroyos where water flow is restricted to flash floods or intermittent events, this principle of hydraulic gold deposition is more erratic. (I'll cover gold deposition in these arid locations in a future post, so stay tuned.)
Clean Cracks and Crevices Thoroughly
OK, let's say you are working a gold-bearing stream and have uncovered some good-looking bedrock (i.e., bedrock with rough, broken features and crevices perpendicular to the stream flow) in a low-pressure part of the stream. Time to put on your gloves (because most bedrock will "slice and dice" hands and fingers), break out your array of crevicing tools, and get to it. Be thorough and clean out even the tiniest cracks and crevices until they are sparkling clean. If you must, use a prybar or crackjack to break them open. Take every bit of material you have recovered from top to bottom and dump it into your gold pan or a 5-gallon bucket. And if, as you do all this, you start to see bits of old lead bullets and fishing weights take heed. This is one of placer gold's signature signs. Why? Because lead's specific gravity is quite close to gold's. Get the picture?
Look for Lead, Nails, and Oxidized Iron
Another portent to look for anytime you are placer mining is rusty (oxidized) iron. Especially items like old square-headed nails, rusty iron bolts, fragments of oxidized metal, or better yet, conglomerations of oxidized nails and iron pieces fused together into masses of various sizes. Examine these latter very closely, for sometimes placer gold flakes or even nuggets can be bound up in these conglomerates (I can tell you about some pretty amazing finds in these). The rusty iron, like the lead pieces, is a sign that you are on the right track in terms of where the stream's gold is being deposited. But I must pull back the reins here a bit. Remember that these pieces of lead and rusty iron are signs and portents, not guarantees.
Think on what I have told you here the next time you are out and about. It may just make your day.
(c) Jim Rocha (J.R.) 2008