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Red Dirt and Desert Gold?


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Just was wondering why so many desert prospectors find good gold in red dirt/rusty quartz? Especially in Australia and Arizona deserts? I know the red is iron but whats that have to do with gold? I am sure not all reddish/orange  dirt has gold so are there tricks you guys use besides just detecting and sampling to find the good gold bearing red dirt? In Indiana we look for bluish clay layers along the creeks/under rocks which can have gold bits resting on top of them, a false bedrock I guess.

 

-Tom V.

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There are vast regions where gold is found and the soil is not red. Very rare thing in Alaska for instance. Much of the bedrock and soil there is featureless shades of gray. Similar to New Zealand. Lots of slates, shales, and graywacke.

It is partly related to the bedrock but also to the age of the topography. Iron mineralization tends to accumulate in surface soils over time, and so old land surfaces tend to be rich in iron if there is iron in the underlying bedrock. The northern US, Canada, and Alaska were all subject to recent glaciation and so land surfaces and soils are almost new in geological terms. Australia land surfaces are just the opposite - very ancient. You can mine iron just about anywhere in parts of Australia.

When gold is traveling in solution far underground iron tends to act as a precipitate and so very often gold and iron mineralization go hand in hand. Not always, it is just a generality. Gold can be found in very pure white quartz, but that would be the exception more than the rule.

Chris is the real expert on this stuff so hopefully he will show up but I think he is busy with the family this time of year. But it really does not have to be very hard. All you have to do is what you have done - just a little research to find out where and in what kinds of rocks gold is found in your area. Then go look there. My methodology metal detecting is very simplistic. I get a map of known gold locations and if there is a cluster of them in an area then I want to hunt in that area. If they seem to lay out in a straight line, then I want to hunt along that line. It does not have to be any harder than that.

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But if you are in an area with no known gold and the signs look good anyway,like tons of rusty hotrocks and your VLF detector chattering constantly,should you be looking for gold? I found an area like this and recent research tells me there was an iron mining prospect there 125 years ago.  

    I wonder if old Bog iron areas might contain gold too? Where were they found and why was it called Bog iron, something about rusty red areas in swamps I believe? Gots to find new strikes.Am sure the old timers did not find all the gold hotspots? Midwestern US  states are gold poor except glacial gold in small amounts , so need to think outside the box.

 

  In a creek in central Illinois, my friend found an area with some shale bedrock, tons of mud in most of the creek bottom, but we struck/dredged up gold anyway by a farmers wing dam on said creek and lots of black sand . We were within 40 feet of numerous RUSTY red football size rocks on the creek bank at the time. No known gold location history thereabouts .

 

-T

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Iron occurs in way more places than gold. Way more places. Just because iron was mined someplace says nothing to me about there possibly being gold there. I would caution you against underestimating what the last 100 years of prospectors have already done. But yeah, if I have the time I will hunt a place just because it looks good. The time thing being the limiting factor.

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The association of gold and iron is an important one. Nearly all gold deposits form from hot water solutions underground which contain gold and circulate to move gold from one area and concentrate it in another such as in a vein. There are several different chemical mechanisms which cause the gold to come out of solution and precipitate, and one of these is contact with iron bearing minerals. The reaction of the watery gold solutions with iron bearing minerals causes the gold to come out of the solution and form metallic free gold, including nuggets. Sometimes the gold comes out of solution for reasons which have nothing to do with iron minerals, but sometimes it is the iron.

However, this is not a universal situation that wherever iron exists there will automatically be some gold. In some places where gold bearing deposits are eroding on the surface of the ground, the rust colors caused by the weathering of iron minerals can be a good indicator that gold may be present. In other places, - the vast majority - rust colored mineralization means absolutely nothing. Iron is the fourth most common element in the Earth's crust and appears all over the place. Gold is much, much rarer and appears only in a certain few places.

Lots of new prospectors would like to find some universal rule for finding gold, like if the soil is red, you will be able to find gold there; or if there is quartz vein material on the ground, there will be gold most of the time; or where if you find a contact of two different types of rock there will be a gold deposit at that place; or if you see bedrock along a stream, there will be gold on the bedrock. These are rules which work fairly well in certain places, but only in those places and they're far from universal. So you just have to learn which rules work in which mining districts and with which kinds of deposits. It's more work but that's just how gold is. What works well in your location is what works well in your location and not necessarily something that will work in other places.

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So much for hard and fast rules on gold locations then.Back to the old adage of gold is where you find it I guess?

I often also wonder how the ancients located metals deposits 2000+ years ago? The Romans were fond of lead pipes for water delivery for instance but how did they even know about lead in the 1st place or where/how to find and mine and smelt it? Ditto for gold,silver,iron,copper? There were no reference books, heck they were using stone and clay tablets for writing materials back then. And yet, most major ancient cultures had gold ,silver,bronze, iron artifacts,coins,weapons, etc?

 

We have it lucky with the inventions of paper, printing presses, computers and such...

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I'd like to add that most gold in the mid-west, in this case Indiana and close by states is not native gold, it was deposited by glaciation, so the gold originated in Canada an areas further north, so other than gold will be low pressure zones of streams, etc. all other rules of thumb on where gold is found goes out the window, the one rule of thumb for glacial gold is to look in drainage areas where there is glacial moraine that is your best chance of finding gold in the mid-west.

 

I would recommend if you haven't read it, is to get Chuck Lassiter's book..."Midwest Gold Prospecting", one of the best books out there for finding glacial gold, he lives and does a lot of prospecting in Indiana and considered to be the best authority on gold prospecting in the mid-west.

 

http://www.midwestprospector.com/book.html

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So much for hard and fast rules on gold locations then.Back to the old adage of gold is where you find it I guess?

I often also wonder how the ancients located metals deposits 2000+ years ago? The Romans were fond of lead pipes for water delivery for instance but how did they even know about lead in the 1st place or where/how to find and mine and smelt it? Ditto for gold,silver,iron,copper? There were no reference books, heck they were using stone and clay tablets for writing materials back then. And yet, most major ancient cultures had gold ,silver,bronze, iron artifacts,coins,weapons, etc?

 

We have it lucky with the inventions of paper, printing presses, computers and such...

 

Don't underestimate the technology or creative ability of cultures thousands of years before our own (the Chinese had paper and the Egyptians wrote on papyrus thousands of years before we had books). If you've ever seen any of the gold artifacts from ancient Colombia or even Egypt, the crafstmanship is staggering. As for how they found it, probably like the earliest prospectors in America or anywhere else. You see something gold sparkling in a river, you search the river and begin to find more and larger pieces. Persistence (or more likely hunger) eventually leads you to the source which is probably somewhere up in a mountain. From then on you have to dig. If you were a Roman emperor you'd have just thrown several thousand slaves at it and sat back waiting for all that gold to come rolling in.

 

Lead may have been a by product of gold mining since it is one of the few metals heavier than gold and is sometimes found together with it. Same goes for the other heavier metals like copper, silver and to some extent iron. But iron, as Chris said, is much more abundant. In fact for every 100,000,000 atoms of iron in the Earth, there is just 1 of gold. That's what were up against!

 

People are like magpies, we always have been and always will be. We are attracted to shiny things, and when that shiny thing looks like the sun then it takes on a very special importance. At least it would have done in ancient times.

 

As for where to find it now, the advice from Chris and Steve and probably many of the others on here will be very useful. A bit of homework will save you a lot of time and digging in vain. Study geological maps of the area, see how old the rocks are, look at the features, are there mountains, faultlines, ancent riverbeds etc. Talk to people and find out if anyone has found gold in the area before, or look in the library. Even online. If there is a river in the area find out where the source is. If it's high up in a mountain chances are it has carried gold downstream, or may still be carrying it. Look at the rocks around you. If they are igneous rocks like granite then there was once an intrusion (or extrusion) of molten lava in the area. That could be a source of gold. All of these are just nudges, you have to follow your nose a lot of the time, but the surest way to find gold is to look where people are already finding it. You'd be surprised how much gold gets missed.

 

Oops, that was a bit longer than I intended!

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Yes, I have Chucks book and know him personally, even contributed some photos in the book of galena ore I metal detected in sw Wisconsin. Just found some photos of Chucks old 4 inch dredge when we were mining together at a secret spot on Big Pine creek by Attica,Indiana  back in 2004. I seem to recall he dredged up 2 gold rings and 11 small gold nuggets that day and numerous small copper nuggets and how I envied him being able to go underwater with his hookah setup to get that better gold...

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Basalts are one of the big contributors to our red colour here in OZ, but you have to be picky, surface generated basalt flows can weather into blood red soils which are very fertile, the ones we want for gold mineralisation are the sub-ducted basalts that have been metamorphosed into different rocks such as our atypical greenstones of West Australia etc. Basalts can be very iron rich, and a major contributor to gold mineralisation here in Australia.

 

Once again Chris is the main man for this discussion.

 

JP

 

To view some good video material Chris, Steve and I created on the subject go to the link below.

 

http://www.minelab.com/aus/treasure-talk/the-west-australian-adventure-video-blog-part-6

 

 

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