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Coarse Hillside Specimens


adam

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At least we now know where black sand comes from and that it's not just pixie dust.  (Any undefined means of working magic, in a metaphorical sense) :)

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  • 1 year later...
On 9/9/2018 at 6:07 PM, BMc said:

 

Again: To paraphrase Jim Straight: "If the old timers found iron nuggets in the wash, they would search for nuggets up on the ridges"

I didn't make this up. 

OK, Anyone want to identify the dark iron looking mineral substance in these photographs that happen to be magnetic (including the two smaller ones stuck to the magnet) and they also just happen to give off a LOUD! signal when a VLF coil is passed over them? Anyone want to venture an opinion as to where "black sand comes from" Has anyone seen Iron Dikes (or iron nuggets) in AZ (or anywhere, (except NM), where obviously they don't exist? :)

The two combined large specimens came from the Bradshaw Mts. The one on the left weighs 11 lbs, the flatter one on the right weighs 9 lbs. I didn't weigh the smaller ones. Usually I find the smaller and even larger marble size ones in certain washes, gully's, rivulets etc.  They come in various sizes depending on the geology of the region. I have found them to be valuable indicators (like finding black sand in in rock form) but they are obviously heavier than individual grains of black sand. HEAVIER? How is that helpful? Oh yeah, gold is heavy. If I don't find any gold in the wash but I suddenly find iron nuggets, then, the basic conventional wisdom of searching the benches, slopes and ridges kicks in. Only in certain areas do I start by detecting in a drainage. If I do, start that way, I usually work the fringes,(erosional zone) of a small wash (I generally avoid large washes altogether, unless mines, or prospect diggings are on the slopes or nearby ) 

I'm looking for those small alluvial in sutu patches (like everybody else), that could still be sitting right where they hatched out from. Prospecting and detecting technique's vary. This is just another way to go about it and yes, I do want the VLF to sound off on the iron nuggets, not the black sand, (obviously)  I don't normally need a shovel or a back hoe, :rolleyes: I can gauge mineralization by sticking a magnet in the ground. Then the Minelab can take it from there.                                                                                                                                                                                                                                                                                              

                                                                                                                            Magnetite photo on far right courtesy of Geology.com.

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ivigo:

The top two photographs are of magnetite that were found with a vlf metal detector. They all meet the physical characteristics that you describe in your post. Mineral iron that (ordinarily) does not rust. The bottom photo was identified and copied from an internet site.

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  • 2 weeks later...

Those are what we call Bog Iron. I think it is different than hematite or magnetite because of the metallic nature of it. It is natural, pure, high grade iron. These two that I have found in Montana, were found in areas with granodiorite batholiths, part of the Boulder Batholith.

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2 hours ago, Goldseeker4000 said:

Those are what we call Bog Iron. I think it is different than hematite or magnetite because of the metallic nature of it. It is natural, pure, high grade iron. These two that I have found in Montana, were found in areas with granodiorite batholiths, part of the Boulder Batholith.

IMG_20200426_024441636.jpg

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IMG_20200426_024227074.jpg

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Are you trying to imply that these are native iron specimens? Native iron is extremely rare. 

Have you done a streak test on rhem.?

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Mineral iron of any type is much different than free metallic iron. 

It sounds completely different than free metallic iron under a detector coil. It is easily differentiated from free metallic iron by streak and luster.

Mineral iron is common. And heavy iron minerals are common in gold bearing areas. It is easily spotted visually as a prospector works an area.

No shovel or backhoe needed. And if a person is digging this stuff with a detector they need to adjust ground balance or get a new detector.

To be clear no one is denying heavy iron minerals do not indicate suitable mineralization for gold. 

The point was that trying to locate this type of rock with a detector is a waste of time. It is easily observed by eye. It slows down the detecting process. And most detectors allow the operator to readily discern these rocks from metallic targets.

There are a bunch of variations of iron minerals. Not all are "hematite" or "magnetite".  We use "magnetite" as a general term for the harder, black or grey streaking minerals that are often magnetic and sometimes show magnetism. But there are other iron minerals that are very similar.

In a formation gold is often closer to the surface. At depth the values often diminish and turn to copper ores or "magnetite". Hard well developed "magnetite" often replaces other metals in a vein formation.

Placers are derived from veins. As these veins erode it frees the gold as well as the magnetite. So well developed magnetite chunks can certainly be an indicator of a placer. 

But once you see this in an area you really don't want to be digging it. Just like stone poodles, an "iron nugget" could only be an indicator of a possible area. Once you know they are there digging them up with a shovel, backhoe or otherwise seems pointless. Digging mineral iron or focusing on the poodle could only slow the process of finding gold nuggets.

I dig heavy iron minerals once in a blue moon. Even with a PI you get a hunk of mystery mineral that will give a fairly good response. And in some areas rocks like this are common. It may certainly be true these areas may be potential placers. But digging a piece of it has never given me a thrill. And I usually try to tune that crap out if possible.

 

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In highly mineralized areas (outside of New Mexico where magnetite "iron nuggets" either don't exist or are not recognized by some), say, Arizona and Wyoming for example, there are areas of sub-surface mineral iron deposits that consist of larger and smaller pieces which, depending upon depth and other factors, can sound suspiciously similar to gold,  The choice may be either to dig or not dig the signal. In a wash or area that is producing both iron and gold nuggets, 20 plus years ago, when the above magnetite pieces were found, the Gold Bug-2 was being used to help locate these areas to then be exploited with ML SD type detectors, with good success. They don't seem to be visible through the alluvium.

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On 9/8/2018 at 2:27 PM, Capt.Obvious said:

Nice pieces adam. bet the source isnt far away

Thanks Capt. Obvious.  :4chsmu1:

 

Nice pieces Adam and Boulderdash  :thumbsupanim   

 

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I'm not sure if they are native iron. I agree with you looking for iron nuggets is probably futile. I'm just saying his pieces could be bog iron. Looking for iron mineralization to determine if an area is mineralized is a good clue. With that you will have alteration. I don't know about all hard rock gold deposits, in regard to clues but iron is big with locating gold in gossans and also very big with skarns. A very big clue for gold skarns is Garnets. Garnets are almost always present within the skarn. That's all I'm saying. The iron chunks I found in the photos came from a granodiorite intrusive formation, part of the Boulder Batholith near the top. They overloaded the detector. There are so many types of hard rock gold deposits and I certainly would not rely on just iron nuggets to point me to gold. Many clues have to be put together to point you closer to where the gold is coming from.

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I get what you're saying. My point was: If a well known Geologist suggested that if iron nuggets were only being found in a particular stretch of a certain wash, that it would be logical to detect the slopes and ridges, benches etc. above where they were found, as a proven method of possibly finding gold (because it had been done in the past), I would probably be inclined to pay attention. Especially if it happened to be Jim Straight.

Pretty sure I would try it, no matter who suggested it, if I respected their opinion. In the area where the larger pieces in the photo were found, I was new to the area and discovered that there were massive sub-surface iron dikes. I eventually ran across some of the iron outcroppings, not gossans per se. Good gold was also being found in the area so I alternated to an SD 2200 which ignored the iron (but not some of the hot rocks) I still used a VLF in new areas, under certain circumstances, to check for iron nuggets. I learned that if I only used my SD I wasn't locating any iron. Like with any/most techiniques, it's not a panacea or sure thing, but just something else to keep in mind when out there trying to put together pieces of the puzzle. 

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I completely see what you are getting at. However keep this in mind, learn what type of life deposit it is specifically, know what are the other rocks are, that are associated with that specific type of deposit. Look for as many of those clues together within an area and focus your effort there. The other thing to think about is time. Do you have the weekend or two weeks to search. If you have a weekend to search, then it may not be time well used looking for iron nuggets. Remember gold is the target, and gold pays the bills or at very least is the target that makes the trip worth taking, not iron nuggets. Also to get a really good mental picture of what is taking place in an area, can take a really long time and sometimes without someone litterally taking you to THE SPOT, you can have many trips of not finding any gold at all.I have one spot I go to that it took 17 years before I found my first nugget in the area. And it is this year that I believe I have the area pretty well figured out. Next weekend will be the weekend to prove my research and lightbulb moment right or wrong. But with what I have figured out and running it by the Chief Mining Engineer with bureau of mines and geology, I am told I'm looking in the right spot.   With this spot you have to be within 3' of the contact. Past that point the gold disappears. It just depends on your area. Learn what direction the contacts go and work in those directions. If I were working your area you are talking about I would be finding out more clues that are stronger indicators of gold, putting them all together, get on goggle Earth and stare at all areas until the the lightbulb goes on, then I would talk a pulse induction as the main arsenal to locate the gold. But that is just me. Good luck and if looking for the iron nuggets doesn't lead you to the gold then maybe give this a try.

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2 hours ago, Goldseeker4000 said:

I'm not sure if they are native iron. I agree with you looking for iron nuggets is probably futile. I'm just saying his pieces could be bog iron. Looking for iron mineralization to determine if an area is mineralized is a good clue. With that you will have alteration. I don't know about all hard rock gold deposits, in regard to clues but iron is big with locating gold in gossans and also very big with skarns. A very big clue for gold skarns is Garnets. Garnets are almost always present within the skarn. That's all I'm saying. The iron chunks I found in the photos came from a granodiorite intrusive formation, part of the Boulder Batholith near the top. They overloaded the detector. There are so many types of hard rock gold deposits and I certainly would not rely on just iron nuggets to point me to gold. Many clues have to be put together to point you closer to where the gold is coming from.

The magnetite pieces in my photos streaked black and are very heavy and strongly magnetic. Doesn't meet the description of the properties of "Bog Iron" or Goethe, IMO. 

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Bog iron is a concretion formed from iron rich solutions. Definitely not a gold indicator. Quite the opposite. It is sedimentary.

Magnetite on the other hand is often formed in polymetallic veins and could be associated with a gold deposit. Or not. Hematite gossan  is commonly associated with gold and the most common "indicator" a prospector looks for. Pyrite pseudomorphs are almost a guarantee of gold. 

Either way, the best indicator of gold is little pieces of gold. Not pieces of iron.

You should dig all targets. And even obvious hot rocks that may be obscuring a signal. But digging noisy slingshot ammo will not fill the poke no matter how many you dig. 

 

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1 hour ago, Goldseeker4000 said:

I completely see what you are getting at. However keep this in mind, learn what type of life deposit it is specifically, know what are the other rocks are, that are associated with that specific type of deposit. Look for as many of those clues together within an area and focus your effort there. The other thing to think about is time. Do you have the weekend or two weeks to search. If you have a weekend to search, then it may not be time well used looking for iron nuggets. Remember gold is the target, and gold pays the bills or at very least is the target that makes the trip worth taking, not iron nuggets. Also to get a really good mental picture of what is taking place in an area, can take a really long time and sometimes without someone litterally taking you to THE SPOT, you can have many trips of not finding any gold at all.I have one spot I go to that it took 17 years before I found my first nugget in the area. And it is this year that I believe I have the area pretty well figured out. Next weekend will be the weekend to prove my research and lightbulb moment right or wrong. But with what I have figured out and running it by the Chief Mining Engineer with bureau of mines and geology, I am told I'm looking in the right spot.   With this spot you have to be within 3' of the contact. Past that point the gold disappears. It just depends on your area. Learn what direction the contacts go and work in those directions. If I were working your area you are talking about I would be finding out more clues that are stronger indicators of gold, putting them all together, get on goggle Earth and stare at all areas until the the lightbulb goes on, then I would talk a pulse induction as the main arsenal to locate the gold. But that is just me. Good luck and if looking for the iron nuggets doesn't lead you to the gold then maybe give this a try.

"I completely see what you are getting at"

Sorry Reese, I don't think it's quite clarified yet. Maybe what's been mis-understood is, I don't just set out to hunt for iron nuggets exclusive of gold!  All the other things you mentioned applies. But what I was stating, was simply how I responded when finding them in a wash! That's all. If they are there, fine. Not there, fine too.

I am encouraged when finding iron, especially of the rusty vuggy type that may be associated with an insutu deposit. But it should be obvious, the object of detecting for gold is, the gold!! Personally, I look for all the many other indicators that are basic in gold hunting including, alteration and contact zones, fault lines, rock types, direction of strike, and a bunch of other things that might point to gold, but if I start finding iron nuggets, I would probably go ahead and check up hill to see where they came from. 

But that comes after hours, days and sometimes weeks of research, acquiring the various geologic maps, claims research, mining record research and a "hundred" other things That's if I'm going to a new area. I think you were initially led astray by BRB in his comment: "The point was that trying to locate this type of rock with a detector is a waste of time. It is easily observed by eye. It slows down the detecting process. And most detectors allow the operator to readily discern these rocks from metallic targets"

This comment missed the point entirely, and is gratuitously  mis-leading IMO, when compared to the single concept which I have laboriously tried to explain. 

Good luck with your 17 yr search and please keep us posted on the results.

Mac

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11 hours ago, Goldseeker4000 said:

I stand corrected on the magnetite and hematite.  And it is not pure it has other things included in the make up.

See what I mean Reese. Take a look at BRB's post:

"Either way, the best indicator of gold is little pieces of gold. Not pieces of iron"

"You should dig all targets. And even obvious hot rocks that may be obscuring a signal. But digging noisy slingshot ammo will not fill the poke no matter how many you dig"

Reese, sorry to say, there is a long history which, unfortunately, you were not aware of, and got sucked into the middle of it.

Best, 

 

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A novice question..

Does Iron stones come from out of the ground in the areas found or would they come from a event and washed  into a ravine from else where ? Possibly some distance away from another place and source  ?

Edited by H-2 Charlie
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7 hours ago, H-2 Charlie said:

A novice question..

Does Iron stones come from out of the ground in the areas found or would they come from a event and washed  into a ravine from else where ? Possibly some distance away from another place and source  ?

The smaller iron stones/lode stones that I have found are usually in a wash, in compacted gravel. They come off of a hill side, or erode out of the bank, like gold does, since they are heavy. The larger specimens, probably come from association with volcanic intrusive events, I believe, since you find them in areas where there are ironstone outcrops. 

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