Wednesday, February 12, 2014

Gold-Bearing Bench Gravels (Part 3)

(Bench gravels often provide visual clues.)

Getting a handle on the gold possibilities contained in bench gravels isn't always easy, but these visual clues and other assorted and sundry tips may help.

Visual Clues

Although some "experts" will take issue with this, it's my contention that certain visual clues can help you find which bench gravels or sections of benches hold the best gold potential. Remember, for what it's worth, I'm speaking here from a small-scale mining and prospecting standpoint without the benefit of advanced degrees in mining engineering or geology.

Here are some potential visual clues that may lead you to better bench gold:

1) Gravels that are either moderately or strongly consolidated (or that display a mix of the two).

First off let's discuss what consolidated means in this context. Essentially I'm referring to how tightly packed the gravel and rock contained in a given bench or bench section are. Although each bench gravel location is unique and some are better than others in the placer gold they contain, I can tell you this for certain: I've never found much gold in benches that were loosely consolidated, especially if they contained little in the way of what I term good-looking "dirt" and instead held lots of blonde or "blow" sand. If a bench crumbles easily under the single blow of a miner's pick or you can shovel it without much problem, then I'd classify it as loosely consolidated as well. Now this doesn't mean loosely consolidated benches can't contain gold...they do. But in my experience the best bench gold recoveries I've made came from moderately or strongly consolidated gravels. (In other words, just like every other aspect of small-scale gold mining you're not going to get off easy working bench gravels!)

2) Gravels that display a range of sizes and shapes, as well as larger rocks or boulders.

This is a very important visual clue in all aspects of gold prospecting and mining and not just for benches. The best benches (like better gold ground everywhere) will contain a wide assortment or variety of gravel and rock sizes, including those that are well rounded as well as those that are coarser or angular. I can't think of one good bench I've worked that contained gravel and rock that were all close to the same size, shape, or level of wear or coarseness. (You "newbies" out there take note and file this info away for future reference.)

3) Gravels that indicate the presence of natural or artificial oxidation.

Most of you already understand the relative importance of iron sulphides and other forms of oxidation in the gold mineralization process. In a similar manner, the presence of rusty red or reddish-orange streaks, layers, or rocks in bench gravels can often be a signpost to gold (and good gold, for that matter). Laterite or other iron-rich soils are often a giveaway in fracture or contact zone regions, as well as in many other placer or lode mining contexts. What's artificial oxidation? The rusting out of man-made iron objects or pieces of those objects (nails, hinges, nuts, bolts, old cans, whatever...) and subsequent iron staining of the localized area(s) around those objects. Keep a sharp eye out also for the fusing or clumping together of these sorts of objects in benches or bench sections because in some instances there'll be gold within that "clump."

Gold Panning Kits
Mining Equipment
 
Yep, I hear some of you right now. "Well hell, if there's man-made iron pieces in those bench gravels then they've probably been worked already and aren't going to be worth a shit." Reasonable conclusion, by the way. But worked already or not, I'm here to emphatically state that if you walk away from visual clues like this one in benches (or in any other small-scale mining context) you're going to end up crying the blues and wishing you'd listened to me. Some of the best gold I've found over the course of nearly 36 years was found by following this oxidation visual clue, man-made or not. In benches or elsewhere, Ignore it a your own risk. (I can't be any clearer than that.)

 (Slight oxidation is apparent in this bench.)

There are more visual clues to come, so stay tuned.

(c) Jim Rocha (J.R.) 2014

Questions? E-mail me at jr872vt90@yahoo.com

8 comments:

  1. JR. I was just in the desert in central az for two days prospecting. And I can say firsthand that your description of the hard packed conglomerates holding gold versus the loose gravels was spot on. I finally found the paystreak two hours before I had to leave. Hopefully it will still be there when I go back.




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  2. Thanks for the back up Gpster. I appreciate it. Best of luck on that bench pastreak! J.R.

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  3. Jim, great post here! Boy how I wish I could drag you around some of this country here! There are several spots that I have tried that look about like your pictures,but I have not found the slightest speck of gold in them. I think it is there, but I don't know enough to find it. I can't get there now, but when I do, I'll send a picture. Maybe you can give me a pointer. On a personal note, I finally got your gift finished......it's only been 3-4-5 years now......OK, I'm not speedy! Will you be home next week? I would hate to have it stolen off your porch.(my Grandparents Christmas present was) Anyway, let me know and I'll try to get it mailed tomorrow. Gary

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  4. Thanks Gary. I'd like to get up into Idaho gold country one of these days. Thanks for the gift...I work each day but no worries about getting anything stolen where we live (knock on wood!). Send me an e-mail with your snail mail addy and I'll ship you one of my small nuggets. Best, J.R.

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  5. Loving this stuff JR, I am about to head off to my lease for the next 7 months or so in the outback. All fired up after a break and exited like a kid to get back and get stuck into it. These posts are perfect timing I have been taking lots of notes old mate. Will send you pics of the nuggets and gold. Will be tying a Wilfley table this year as well should be very interesting.

    GS

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  6. Good on ya Mate! Glad this stuff is helping. Wish I was heading out into the Outback with you, my friend. Bes tof luck out there! J.R.

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  7. J.R. Thank you so much for your great web site, so many of questionable mining thought are answered here. I do have a question on beach mining in Nome Ak. I am sluicing and when I dig down I hit a thick blue clay, would the gold have worked its way under the clay or would the gold bearing material been before the clay? Or would it not have penetrated the clay and be above it ? I am heading back this summer.

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  8. Hey Fred! You're more than welcome. You ask a terrific question here about clay layers. When you read the accounts of the old timers during the CA Gold Rush they talk a great deal about clay layers and getting gold beneath them as well as on top of them. I worked the Motherlode for many years but never found gold below a clay layer...always on top. However, I never dug down to great depth through successive clay layers either. So I would check below the existing layer but would not waste a lot of time in that regard. Best, J.R.

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