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How do they locate gold?

  1. Aug 22, 2012 #1
    Good day sirs.
    I was wondering, how is gold located?
    I mean, do they use any machine to locate it
    I am referring me to depths of over 10 meters up to 2 kilometers
     
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  3. Aug 22, 2012 #2

    Simon Bridge

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  4. Aug 22, 2012 #3

    turbo

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    Placer-mining is popular. As the sizes of the nuggets increase, keep heading in that direction to find the lode. Panning is popular here in Maine, and I ran into a few guys from a fire department that take their vacation together yearly and hand-dredge a river in Byron. They have a mechanical separator that looks pretty cool. One of the guys told me that they could usually get enough gold out of the river to pay their vacation expenses. That's a good deal. They get to "get away", entertain themselves with the possibility of hitting a "honey hole". All good.
     
  5. Aug 22, 2012 #4

    Simon Bridge

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    Pretty cool ... do any of these methods uncover gold deposits more than 10 meters deep as per OPs question?

    I have a feeling that it is mostly guesswork relying on geological processes to bring some of the gold to the surface in a way that hints at a bigger load still down there.
     
  6. Aug 23, 2012 #5
    That is very cool dude.
    Ok, what if i build a metal detector, can i "manipulate" the metal detector so that i can get readings below 10 meters?
     
  7. Aug 23, 2012 #6

    Simon Bridge

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    Then you'll get returns off any metal in some range below 10m.
    Hmmm ... wonder how strong that would have to be to get a decent return through 10m.

    You specified "gold", anyway. There are a lot of other metals in the ground.

    You can also look for seams seismically or use ground penetrating radar, if all you care about is "is there something under there to dig up?"
     
  8. Aug 23, 2012 #7

    turbo

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    @OP: I doubt that there there is any electro-mechanical equipment to give you an advantage at any depth. A metal detecter used in an alluvial flow can help you find dust and nuggets. Gold is very heavy, so the bigger the nuggets, the closer you are to the lode.

    You would be best advised to learn the geology in your locale. Around here, gold is often found intermingled with quartz. YMMV.
     
  9. Aug 25, 2012 #8
    To explore for deposits using placer mining techniques, you follow a watershed containing placer gold upstream. Pan the gravel beds in the river, and the deltas deposited by each stream entering the river. If you obtained traces of gold in one stream but none in the next streams upriver, you've passed the source. Go back and follow the gold bearing side stream(s).

    At this point, you look for evidence of volcanic rocks, especially evidence of hydrothermally deposited minerals, since gold is usually deposited by hydrothermal vents: those are the 'black smokers' one seas on the ocean floor.

    Japanese geologists, in fact, found one hot smoke that is depositing a rich seam of gold somewhere off their coast: I saw the colour video of this, but I don't know the scale of what I saw. This deposit will probably be left where it is since the Japanese won't say much except that it is more than 5,000 M below sea level. Therefore It would cost more to mine the deposit than it's worth. *

    A rule of thumb is that one ~might find~ gold in a stream or deposit which has black sand (magnetite) but one will never find it if there is no magnetite (FeO3.)

    Metal detectors can't differentiate very well between metals, as far as I know.

    *Ordinary sea water has gold in it, and it can be recovered if you know how. But the latest figures indicate it would cost in excess of about $3500 an ounce to recover a mineral worth (now) under $1600/ ounce, and the price will probably drop in the future. Again, not cost effective.

    Another way to find gold is by biopropspecting: some plants are known to accumulate metals in their leaves and stalks, and one tends to accumulate gold. However, I don't know which plant this is. A search for 'bioprospecting, gold' may provide an answer.
    In this method, certain plants are havested, dried, and burned (probably in an oxygen-low chamber), and the ashes are analyzed for metal content. I'm pretty sure this is too expensive to do more than find indications of gold showings.
     
    Last edited: Aug 25, 2012
  10. Aug 25, 2012 #9

    turbo

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    That's pretty much the procedure for placer-prospecting. If you can find a stream that yields nuggets (not just dust), follow that upstream and DIG in the gravel beds downstream of boulders. You might not find a lot of gold that way, but is surely more profitable than mining hard-rock and just hoping. Let mother nature do the hard work for you.
     
    Last edited: Aug 25, 2012
  11. Aug 25, 2012 #10
    There was one guy who moved to Spences Bridge, B.C., in the 1930's or so, and found a cabin by a creek running out of the mountains. He set up a flume and divverted water from that creek into a barrel. The barrel was line with a wool blanket, and every few days he'd take the blanket out and put another one in. He'd wash the blanket in a big tub, and this released all the sand and such that was captured by the blanket. He'd then pan that and recover the fine gold dust in the sand, what we call 'flour gold' in this country. He managed to support himself by doing this for decades.
    The down side of this, compared to finding nuggets, is that the old timers used mercury to amalgamate the gold. Nowadays one would use aqua regis or something of that sort. I watched a goldsmith use it (or nitric acid?) to recover gold, but I haven't bothered to research the chemistry behind it.
    To purify the gold, melt it and alternately use baking soda and Borax powder as fluxes. After a few go-rounds, you'll have 24 carat gold.
     
  12. Aug 25, 2012 #11
    Because gold is a very "money giving" substance.
    And i have a taste for geology
     
  13. Aug 25, 2012 #12
    Ok mate, i will do that ;)
    I don't know much about finding resources "hidden".
     
  14. Aug 25, 2012 #13
    Thanks a lot for your answers.
    But that doesn't clarify the answer
     
  15. Aug 25, 2012 #14
    For mining applications, a small drilling rig is often used to drill small sample holes to test how much gold is likely in that specific area. Geologists will also attempt to locate veins of gold ore or rocks and minerals that are commonly found with gold. Magnetic sensors could also be used to detect large amount of minerals in the ground. For small scale prospecting, learning about local geology and how hold forms and what it is commonly near along with a sensitive metal detector could work. They can differentiate between different metals. Otherwise a small drill on a truck taking core samples or just digging a hole may be what you want.
     
  16. Aug 25, 2012 #15

    Evo

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    Please post the link to the paper(s) on this. That would be helpful.
     
    Last edited: Aug 25, 2012
  17. Aug 25, 2012 #16

    Evo

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  18. Aug 25, 2012 #17
    The information comes from my own knowledge and interest in mining and prospecting, I have studied how mines work and how to mine, once had an idea to go mine gold in Alaska or elsewhere and am interested in resource excavations. There are no papers that I can link too and if it is in someway violating physic fourm rules please tell me.
     
  19. Aug 25, 2012 #18

    Evo

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    We just prefer to have actual references, in this case to see how it's done would've been nice. You stated it was from your own experience, so that's fine, I was just hoping you had more, I've been searching with little results.
     
  20. Aug 25, 2012 #19
    To sample deeper than one can with gold panning and bio-prospecting methods, one uses core drills. These are basically highly specialized 'hole saws'.

    http://en.wikipedia.org/wiki/Core_drill

    See also the core drill illustration about half-way down this page:

    http://atropos.as.arizona.edu/aiz/teaching/nats102/lecture9.html

    These hollow drills provide one with rock samples that can be split and resplit. One part of the core- the ones that show interesting looking mineral samples- is sent to an independent lab for analysis, using either acids or a spectrum analysis machine. Half the samples are kept "on file" by the exploration company. In some cases a second quarter of the samples is sent to another lab for a second opinion. The one half is kept in case the deposit needs to be re-sampled at some point.

    Drill holes are laid out on a grid pattern, with parallel rows of these holes spaced a distance apart on the property. These drill holes can be quite deep, 2,000 meters and more, depending on how much the exploration company wants to pay for.

    This sampling allows a geologist to now create an approximate 3d profile of the deposit on a computer, which in turn gives an approximate volume. That in turn can lead to an estimate of how much ore is in the deposit.

    I have been asked to help a geologist put together a series of study guides about core drilling and the tasks associated with this kind of job. Previous to this, I did some work reading through 3,500 pages of a particular copper and precious metals mine proposal to find out what the deposit contained but the mining company wasn't publicizing. I found worrisome pockets of mercury, and some radioactive minerals. This job was a real learning experience since I had to look up a lot of geological terms and mineral names.

    I now have a much deeper understanding of the geology almost literally under my feet, and it's fascinating stuff. [Vaguely, just a bit west of Kamloops, B.C., and south of the Thompson River.]

    So hopefully this helps explain more about how to find minerals (gold) below 10 meters. My apologies for not quite understanding the question in the first place!
     
  21. Aug 25, 2012 #20
    Add: It's irrelevant, but I have some core samples sitting right next to me. They look for all the world like long 2" diameter granite rolling pins, and I AM tempted to try one for making cookies.
    At least I'm pretty certain they're granite....
     
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