GOLD Geology 101: What Rocks Host GOLD Deposits

I want to teach you some of the rocks that you should be looking for if you want to find gold the first rock I'm going to show you is a piece of granite anytime you got Creeks running through granite see that that's nice red granite in there see that all those little crystals anytime you got water running through granite like this test pan I guarantee you might find some gold there Granite is an ous Rock I know a lot of people out there are going to argue with me and they're going to say no Jeff it's metamorphic remember you got three types of rocks Ignus metamorphic and sedimentary all right next one is going to be Basalt now Basalt is volcanic in nature and what you want to do is you want to break it open take a look inside if you see any green inside start panning that area test pan it cuz I'm telling you there's probably gold there and the last one is this one it's ugly looking red mud looking stuff and it's dried and it's been set down for a long long time anytime you got water running through this it redeposits the gold out of this into secondary forms of enrichment or secondary deposits so you want to pan those areas that are like that I got to tell you about the three s's Shi slate and and shell those three types of rocks are fantastic for gold some produce gold load that is and others a great trap in it like in plaster gold because of the rough edges especially if it's running perpendicular to a wash woo we that's a good place to find gold ain't that R slam all right that's right I'm going to grab this guy right here that's a backpack we're going to go up into the Bedrock cracks some crevices do a little sniping cuz I said it once I'll say it again the best gold you ever get to get is the gold that mother nature put down look at that there's quartz they call that float it's everywhere wow look at this I don't know if you can see that that's nothing but iron that doesn't mean 100% that there is gold here but when you got quartz and iron and a gold producing area chances are there's gold and I got Bedrock here we're going to suck it all out I tell you what that'll work it I'm going take it up to my patting tub pan it out and see if we got any go and see what we get yeah you're going to get wet man that's an awful heavy pan feels like nothing my black sand in there I always find my best goal out in Granite that and layers of decomposing Shi all right come here take a look at this woo man I'm dying woo look at all that black sand that's that's nothing but black sand you see that holy cow come on Baby Daddy needs some gold wo I see a little piece of gold right there's another one right there you see it oh come on come on baby I'm going to shake that down I can't wait come on baby I saw a little woo there you go look at that I got a couple pieces right there I don't know if you can see that see that there's one right there oh yeah woo look at that look at that flake oh you got to be kidding me look at that I got a nice flake right there see that a flake oh that's a big one a big flake see all these little itty bitty flakes in there woo let me see if I can tap that up for you yeah that's what I'm talking about finally I got a flake right there a flake right there oh that's a big one too see that there's a nice flake right there that's a giant one and all these little tin of flakes in there all over the place don't get discouraged have the courage to learn all these rocks on your own for the lure of gold the amount Untold can drive men mad once it's known this is an intrusion related deposit so you have a gantic mass usually in the form of a pluton coming in contact with Limestone and where it's come in contact it's actually changed the Limestone into a metamorphic rock you got hornfel which is nothing more than baked mud and then of course you got scars gold bearing scarns can be very rich the veins are not very deep maybe 120 ft deep they were pulling out $2500 per ton $20 an ounce oh my gosh that's Limestone see that nasty gray limestone in there and wherever you have these contact zones of granite up against the limestone a lot of times the metamorphic rock that's created is is a scarn now there's all types of different scarns out there but the one we're worried about is gold bearing scarn whenever you see Reds like that I definitely sample it Limestone granny I remember that where you get that intrusion if you have any gold inside of the solutions and the steams inside that pluton what will happen is is that the Limestone will change the pH balance and then what will happen is the gold will start to drop out a solution and at the contact zones a recrystallization process of metamorphism and so then you're going to get a layer of scar in there at the contact this is what's left of a Trestle what they would do is they would build these trestles way out into the middle of no then they would slowly dump the rock dump the Rock and that's how they'd get it out away from the mine and then that's how you see these big nice flat piles what some people call tailings but they're not they're called Mind dumps and the way they got them out here was these trestles and buried inside of all this is a whole bunch more of these that's how they built these big Bridges and then they could just keep dumping and dumping and dumping and they start another one and another one look at that isn't that some nice Granite it almost looks like Granite diorite which is a mixture of granite and diorite but I don't think it's got enough horn blend in it to make it that see all that red material remember I told you a red scar now I got to emphasize something real quick okay cuz I know a lot of you might be confused but scarn is not the same as lionite remember that not all red material is the same lonite is usually a byproduct of sulfides that have oxidized out the sulfur and left behind iron oxide and gold if there's any gold in it and of course it's all boxy looking so they call it box works this is scar this is a totally different animal they both can have gold in them but they're totally different I just wanted to emphasize that because some people will see it gosen and think it's scarn no it's not there was three miners that were staying here to oversee the mine When Buyers were shifting hands or trading hands on this mine so they kept three guys three miners out here Gordon plate and cook were their name last names Indians came in here and they saw the white man and of course they didn't like the white man being in their land so they killed cook outright and the other ones Gordon and plate they got real scared and I would be too you know so they took off uh headed west on the other side of this mountain they ran so far out there think thinking they were getting away from the Indians but you know what they forgot about that's right they didn't bring any water with them and they started to go insane because they couldn't come back here and there was no water out there so they figured the only way out was to put a bullet in their head and that's what happened they killed themselves it might look peaceful out here right now but back then it was a hostile land anyway I just wanted to give you a history of this place y see this that's Limestone big old hard nasty Limestone see this that's that decomposing Granite you see what I see look at these colors see that blacks Reds dark Browns this is what you need to be looking for this is some beautiful beautiful looking scars see that chrys aola in there that you have a lot of your pulfrey copper deposits that produce gold and your scar deposits anyway whenever you get copper in the mix that's always always a good sign I got this beautiful looking scar right there see that what I'll do is I'll sample some of this stuff back here cuz they were falling and see where they St I got a whole bunch of wasp nest in there too you got to be careful with that this is what I want to show you you're going to see these in a lot of your intrusion related deposits that have to deal with gold bearing scars what is it bog iron it's almost 100% iron it's nothing but iron see that's solid iron you find large thick bands of that bog iron and when you do you know you're onto a winner now in my years of experience I found that the best gold is where the vein has a steep dip and then it has a shallow dip and then a steep dip where the vein has that shallow dip you're going to see huge chunks of gold that have formed in there I know it doesn't make sense but it'll actually redeposit in there and you'll find large chunky masses and even wire gold in [Music] there real quick backstory on the place that we're at used to be called the Robinson District it was founded in 1867 they found gold here and they rushed in and they mined it out what's interesting about this place you have a huge P Frey intrusion here and of course on the outskirts of that is what gold deposits and I'm going to talk in great depth about why those deposits are here how they formed and what you should be looking for when you're out in the field now there are 12 basic models of deposition for gold there's a lot more than that but the 12 basic models is all you need to know about and this is one of them this is a pfy or intrusion related deposit also iron oxide copper falls under this category as well around the crot time period you had quartz monzonite intruding into limestone it's a huge pluton now most of the time when you see a pluton in a book it's drawn like an upside down teardrop and that's not what they look like at all they're more tabular nature think of a big water balloon laying on the ground that's what they look like inside the Earth as it comes up to the surface it's slowly cooling as it does so it starts to undergo changes and this is where Bowl's reaction series comes in it's very important you understand that cuz that magma chamber it can do all kinds of things it can turn into all all kinds of things it's starting to crystallize now this was a quartz monzonite stock which is of the Granite family as it was cooling it was fracturing as it was fracturing all these minerals from Down Below in the Melt are coming up and starting to fill those voids that's how you can get pulfrey from granite or from quartz monzonite how it's altered inside the ground now on the outside of this alteration you have other alteration zones that are going on at the same time you're going to have scarn you're going to have Clay you're going to have clay with pyite on the outside of that you're going to have quartz sericite alteration then on the outside of that you're going to have argic alteration so you're going to have all these bands of alteration going on around this guy and this is important for you to know and as it was coming up it was encountering folded beds of limestone and shell which you're going to see a lot in this area as it comes in contact with the Limestone as you know on these intrusion related deposits you're going to have scarn deposits there now scar is a general term and you're going to hear that a lot a lot of your py deposits are going to have scarn deposits associated with them now you have all kinds of scarns out there you've got iron scarns copper scarns gold scarns there's all different types you usually find them a lot when you're dealing with some type of intrusion related deposit but you can also find them in faults and Shear zones and geothermal systems too they're not just isolated to intrusions from ous rocks there's two types of Scar I know this is getting complicated but just stay with me on on this you got oskars and exos scars and the way you tell the difference is like this on an endoskarn the protolith is going to be ous and on an exoskarn the protolith is going to be sedimentary protolith just means Proto being first and lith being Rock so the original Rock before it went through any type of changes now the reason why you get scarns is a process called metasomatism all it means is is that you have a transfer of hydrothermal fluids from the protolith to the wall Rock Rock so you're going to see a lot of that in your USGS report when you see scarn you're going to think of the metotic process now the things you should be concerned with is when you have py copper gold deposits on the outskirts you're going to have tons and tons of scarn even though it's a copper py deposit there can be gold in this Scar and that's what you need to look for also they have gold scarns and they have what's called A reduced gold SCAR Where the percentages are 5 to 15 G per ton and those are mined solely for their gold content now mostly your copper py deposits the gold is a byproduct and your copper and gold scars are going to have a high garnet and pyrine ratio to them not to mention a lot of iron and they're real easy to spot too so when you find them you're going to want to sample them but most of your USGS reports is going to call it a poly metallic replacement deposit that's its technical name of course a secondary enrichment scorn and that's what you're looking for because it can be very rich in some sections depending on where it is how it formed and of course the mineral assemblages that were associated with its formation don't let all those big words fool you it's just scarn it's the red scarn when you find these things you're going to dig down around the bottom here and you're going to pan this out screen it and pan it and check for little tiny like 100 minus mesh gold in there that's leeched out of this thing if there is and you need to start going down underneath it to get to the better gold because most of it's leeched out of this thing for millions of years and you're going to find these on the outer edges of these giant pfy deposits of copper and yeah you're going to get wet some of that ground up gold in there oh that's looking nice what I want you to do is become familiarized with the types of rocks that are in Gold producing districts now in this particular District got a lot of pre- cambering shist shist is nothing more than shell that has been squeezed and heated and of course you know where shell comes from Shell comes from mudstone It's A clastic Rock and as it's pressed and squeeze under low heat you'll start to see micia form in these sheets and bands and sometimes you'll get pyite crystals growing in between these sheets as well a little bit more heat a little bit more pressure and it's changed into slate which is a metamorphic so head has gone from sedimentary to metamorphic more heat more pressure it becomes a piece of shist now shist is easy to identify because it's full AED and it usually breaks apart really easy you can see where a lot of the Micah is starting to form in the foliation now a lot of times you can also have gold that will form or pyite that will form in the foliation now why is this important because a lot of times in your USGS reports they're going to say there's pre- caming shist and right next to it you have quartz and you can see where the shist was up against here and then broke away and you can see I've got oxidation going on in there I've got also Limonite in there and that's what happens when a lot of your pyite oxidizes is you get Limonite that's great news because you want the sulfur to go away you don't want to have to roast it you want mother nature to roast it so when you see that red it could be lonite which is good cuz the gold will be left behind or it could be oxidized hematite or magnetite this is called bull quartz and they call it bull quartz cuz it's baren there's nothing in it along the joints of the quartz sometimes you can have mineralization in there remember you got the three types of rocks sedimentary metamorphic and ous lot of your gold is going to be found in metamorphic rock a lot of it most of your basement rock your continental crust rock is going to be ous and then of course sedimentary if it's under enough heat and pressure turns into what metamorphic you see how that works and also keep in mind that you got two different types of sedimentary when you're talking about limestone and shells one is clastic and one is bioclastic bioclastic just means it's got a whole bunch of seashells and living organisms that make it up that's what limestone is and this stuff is just plain old clastic material that's been squeezed like mudstone but at least know your Basics when you go out to a gold producing district and know what the rocks look like that are hosting the go shape CL into a vessel it is the space within that gives it value set spokes within a wheel it is the emptiness of the Hub that makes them useful be the space at the center be nothing and you will have everything to give to others

Channel: Ask Jeff Williams

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Keywords: Gold Geology 101: What Rocks Host Gold Deposits, jeff williams gold prospecting, jeff williams gold, ask jeff williams, ask jeff williams gold, high grade gold ore, ask jeff williams gold panning, how to find placer gold, placer gold, placer prospecting, prospecting, gold prospecting, mineral exploration

Id: 4AbXOAeO-Lc

Length: 15min 41sec (941 seconds)

Published: Sat Jan 06 2024