Going after Deep Large Gold with a Big Coil


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A while back I found a nice new patch in among some old placer workings and I have been working off and on to clean the area out. It’s a forest location in California. Much cooler temps there this time of year as compared to the Nevada desert and some nice shade to boot. The ground is hard and compacted but its not caliche by any means. I’ve picked up several ounces of nice nuggets with an average size of just under 3 pennyweight, but the spot is mostly cleaned out for now. As a part of this process, I’ve now also cleaned out the trash (which is almost all shallow), so last weekend I went over the area with my biggest coil – a 20 inch mono. The area has deep over burden with good sized gold all through it, so it was a good spot to bring in a large coil. If I could get more depth, I knew I’d get more gold.

Big coils have their advantages and disadvantages. They pick up deep large gold you just can’t see with a smaller coil, and that’s a pretty huge advantage. On the down side, they pick up much more interference than smaller coils, and I find them much more difficult to pinpoint with and so I end up digging much larger holes – and in hard soils that can be a real bear. Its also hard to poke them in among bushes and overgrowth, but this spot has some significant open area among the growth. Still another thing is that you dont want to put on a big coil in a trashy area getting more than one bit of trash at a time under the coil can be confusing.

When I arrived at my spot, I put on the big coil and listened for weak targets. (remember I’d already gone over this spot with a 11 mono and a 17x10 eliptical mono, so probably any targets large and shallow enough to sound off as a strong loud target on the 20 mono would have at least been a weak target on the 17x10 eliptical mono). Sure enough, the 20 inch nugget finder located several weak targets that sounded good in places I’d already pounded hard with the smaller coils. What I did for my own convenience was to dig down a few inches and confirm that for sure it was a good deep target, then I marked the spot. When I was done going over the area with the large coil, I changed coils to my 11 inch mono so I could pinpoint the target more easily and I would not have to dig a giant crater type hole in the hard ground. The strategy worked well. When I dug them out using the 11 inch mono, the first two targets turned out to be deep bits of iron rubbish, but the third was a very nice specimen nugget. It’s kind of a sandwich piece with iron oxides and quartz on both surfaces but a thick slab of gold in between. It’s one of those pieces that are actually mostly gold by weight but still show a lot of host rock. It weighs 10.4 pennyweight – a little more than a half ounce. That’s why I think its smart to have a big honking coil like the 20 inch NF in your arsenal.

The half ouncer was down around 14 inches, and at that depth it was a pretty faint target on the surface with the 20 inch coil - if it was much deeper I would not have heard it. I had dug a 1 pennyweight piece at 6 inches depth about 2 feet away from the location of the half ouncer so I know I had gone over that spot real well with the smaller coils looking for other nuggets close by. I found that 1 dwt piece with my 17x11 mono oval coil and it was at just about the limit of detection as well for its size (I actually walked away from it thinking it was just ground noise).

How deep you might detect a certain weight nugget is of course, a complex question. The soil and the nugget size are important, but some gold sounds off better than others. Mostly solid nuggets are a lot easier to detect than porous ones. The gold from this spot is porous and wrapped around iron oxides and quartz if you look at it under magnification. As a result it does not perform as well as you might expect. The smallest nuggets I have found here weigh just under half a pennyweight. Normally that weight would sound off loudly on a coil like my 11 inch mono, but it was pretty weak even at about 3 inches. I have found plenty of 2 to 4 grain nuggets elsewhere, but not here. Nuggets of about 10 grain size is about the limit there, even with a smaller coil.

Chris

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