(Sharing knowledge is always golden.)
This post is sort of a follow up to my flood layer series but since the topic itself isn't always related to flood layers I think it deserves direct attention of and by itself. So venture forward with me and you'll gain a bit of new mining knowledge. After all, sharing your knowledge with someone else is always golden.
Suggestions and a Digression
First off, let's get something clarified. I'll be talking about hard pack in all its various forms in this post...not true bedrock. Although most of the principles for working various forms of hard pack can be directly applied to working bedrock, there are differences between the two. Hard packs, like bedrock, form impermeable layers to the passage of placer gold ever downward. Unlike bedrock, however, hard pack layers can contain gold within the material(s) that formed them. Most importantly, successive layers of gold-bearing hard pack can exist in both wet and dry placers. Successive layers of bedrock cannot.
(We're not talking here about true bedrock.)
Yes, I'm talking about working dry hard pack layers in this post but don't let that dissuade you wet placer miners out there. Even where running streams exist, dry hard packs can exist above the current water flow or in nearby dry gulches or creek beds. For you "desert rats" out there (and I used to be one of you), dry pack layers can be found in virtually every desert placer location out there. The mixture of raging flash floods, excessive heat, and extremely dry conditions in desert placers pretty much ensures that any mixture of materials (clays, dirt, gravels, etc.) will be a likely prospect for transformation into some sort of hard pack once all that elemental "baking" takes place. Ditto for many dry gulches, creeks, or streambeds in wet placer areas. For example, in the Southern Motherlode Region (starts around Coarsegold, California and then proceeds north to Placerville) the old timers found very rich diggings in smaller gulches and creek beds that were totally devoid of water. This was a two-edged sword for those early Argonauts since it was nigh impossible to work those dry diggings without hauling water or gold-bearing material considerable distances. Those small-scale gold miners out there reading this who live in or near Sonora or Mariposa take note. You might want to forego the main wet placers in your area and start checking out some of those drier locations nearby. Just a suggestion, but I digress...
(Dave Mack of the New 49ers pointing out dry hard pack layers.)
There are tried and true methods for working dry hard packs and that's the core theme of this post. So let's get down to it:
1. Forget the overburden. Well, most of the time anyway. In general, any overburden covering dry hard pack will NOT be worth the time and effort to process (this is true of most wet placer ground as well). If that overburden covering your section of hard pack is shallow just move it to the side(s) or shovel it away and out of sight. Now if you're a paranoid sort and find yourself getting the heebie-jeebies because you're tossing "good" dirt aside go right ahead and sample that overburden to see what it contains, if anything. In most instances you'll be schooled up pretty quickly to the fact that overburden holds little real gold potential. Yes, dry placer areas can fool you in this regard due to the erratic nature of gold deposition in them. I know this for a fact. Sometimes good gold can be found in that overburden but that's a rare event, truth be told. My best advice is, again...don't waste a lot of your precious prospecting and mining time fooling around with overburden. Or, alternately, if that overburden covering your hard pack is only a few inches in depth then just classify it and bucket it up along with any loose scrapings off the hard pack. You can then run it through your dry washer or recirculating processing gear and put your mind to ease about losing any "maybe it's there, maybe it's not" overburden gold.
2. Swing a good gold detector over that hard pack (optional). Use your Minelab, Gold Bug 2 or Pro, White's, Garrett, or whatever machine suits your fancy to sweep the area of hard pack for possible nuggets or accumulations of gold. By the way, the Fisher Gold Bug series of gold detectors has earned an excellent reputation for detecting very small pieces of gold. If you use a machine during this step be alert for signals indicating iron or lead as well, since iron oxides of any sort and lead shot can mean the presence of gold
3. Shovel or scrape away all the loose material resting directly on that hard pack. Notice I used the term "loose" here. One thing you'll eventually realize about most dry hard packs is that they'll have loose material (dust, dirt, small gravel, etc.) still resting on them as well as spots where these same materials are fused together into concretions of various dimensions. This is AFTER you've shoveled or bucketed up the bigger material and overburden. You'll want to run this material, obviously.
(The desert tends to "shake and bake" its own hard pack.)
3. Get down low. You can't be standing tall or plopping your ass on a bucket or camp stool to successfully work dry hard pack after the bigger material has been shoveled away. You gotta get down low, on your hands and knees or even on your stomach in certain instances. You can't work dry hard pack from afar, so remember that key point. Being in close proximity to that hard pack allows you to see what's going on, allows you spot any larger pieces of gold that may get uncovered, and shows you where clusters of dried gold-bearing material are cemented or stuck to that hard pack. Now's the time you want to break out those small tools like a scraper, rock hammer, paint brush, and so on. Oh...and one more item...a blow tube or blow pipe (I'll talk about these things in a bit).
Wal and Liz are a couple of Aussie prospectors and miners who know their stuff, wet or dry, backwards and forwards. In the video I'm about to link you to, Liz is working a section of dry bedrock down low using some small tools, tweezers, and blow tube. Despite the fact that Liz id working true bedrock in a dry area, the manner in which she does work is a good example of how you should approach dry hard pack. The idea here is isolating quality gold, not shoveling massive amounts of dirt and gravel hoping to score. I know this goes contrary to standard small-scale mining theory (even my own), but the fact of the matter is that it's the best way to work hard pack completely and thoroughly, and why you need to be low to the ground.
Here's Liz doing her thing: https://www.youtube.com/watch?v=LQ4Ka_OQuIg
4. Clean that hard pack thoroughly. Use your hand tools to scrape loose or bust up any areas where small concretions have been formed. This is where a blow tube or blow pipe come in handy. A blow tube is simply a small length of flexible tubing you can use for sending bursts of air from your mouth onto the lighter material still resting on hard pack. Just as Lil showed in the video, this helps to expose pieces of gold to view, including flakes, chunkers, and even small nuggets. If you don't have a piece of flexible tubing on hand, a blow pipe can be made from the bottom half of a ball-point pen shell or something similar. After knocking those small concretions loose, use a stiff paint brush to brush the surface of that hard pack clean. All this material should be processed or otherwise checked for gold.
5. Swing a detector again over the areas you've cleaned. After you've done the Liz thing, try swinging a good gold detector (Minelab? Gold Bug? or ??) over the area you've already supposedly cleaned up/cleaned out. It never hurts to make sure things are as complete as you think they are.
(Checking a section of hard pack with the overburden scraped away.)
Obviously, none of this is rocket science. If I had to say one thing to you about working dry hard pack it would be this: "Be meticulous, patient, and thorough. Leave no stone unturned in your efforts. Take your time and do things right, not half-baked or half-assed."
Come to think of it, that's good advice that covers a lot of human endeavors.
Be good to yourself as well as others...
(c) Jim Rocha (J.R.) 2016
Questions? E-mail me at email@example.com