Best coil for copper?????

[fdl]

I have the 705 with the standard 9" 7kHz concentric + the 9" 3kHz concentric & now I would like to add a DD to the mix.
What I'm looking for when I md are copper artifacts.I've been surface hunting in plowed fields for Indian artifacts for years & now I would like to use my 705 in these same fields to locate copper Indian artifacts.So my question is what coil would work the best for finding copper artifacts? The 3kHz concentric I know would be a good choose but in highly mineralized soil I would like a DD. Also,these copper artifacts can be as deep as 15" down AND does ancient copper 2-5 thousand years old have a different signature then modern copper? So my choices are:
#1 the 10.5",7kHz DD
#2 the 3kHz "digger" DD
#3 the 15"Coiltek all terrain-3kHz or 7.5kHz
I can only afford 1 coil so which coil would you choose?

 

[Old Longhair]

If deep is important, then a large coil is called for, so I would say #3.

I don't know anything about ancient copper. Is it pure? Or is it alloyed?
Modern copper isn't pure. As an example, copper pennies from 1864-1962 had varying amounts of a tin alloy.

 

[fdl]

If deep is important, then a large coil is called for, so I would say #3.

I don't know anything about ancient copper. Is it pure? Or is it alloyed?
Modern copper isn't pure. As an example, copper pennies from 1864-1962 had varying amounts of a tin alloy.[/quo

Indians found & then used raw copper that was located in outcroppings most notably in upper Michigan. Is it Pure? They used the copper they found & fashioned it into spear points,axes,celts & other jewelry. So yes,I would say it is pure with no alloys added although they did heat & cool it to pound or form it into what they needed.
As far as which DD coil to choose I settled on the 10.5" 7.5kHz. I would have went with the all terrain but it may be a little to big to swing in tight places(corn stubble, weedy areas,wooded areas). Thanks for the reply Longhair......Al

 

[Old Longhair]

Indians found & then used raw copper that was located in outcroppings most notably in upper Michigan. Is it Pure? They used the copper they found & fashioned it into spear points,axes,celts & other jewelry. So yes,I would say it is pure with no alloys added although they did heat & cool it to pound or form it into what they needed.
As far as which DD coil to choose I settled on the 10.5" 7.5kHz. I would have went with the all terrain but it may be a little to big to swing in tight places(corn stubble, weedy areas,wooded areas). Thanks for the reply Longhair......Al

You'll do well with that coil Al. The spokes on the 15" WOT MKII snag on brush and stubble a lot. It can be done (I have), but in ths case I think that less is more. That coil will hit hard enough on copper, and it will ring up high. How large, thick, and/or deep it is will have a bearing on just where it will ID.

 

[fdl]

Indians found & then used raw copper that was located in outcroppings most notably in upper Michigan. Is it Pure? They used the copper they found & fashioned it into spear points,axes,celts & other jewelry. So yes,I would say it is pure with no alloys added although they did heat & cool it to pound or form it into what they needed.
As far as which DD coil to choose I settled on the 10.5" 7.5kHz. I would have went with the all terrain but it may be a little to big to swing in tight places(corn stubble, weedy areas,wooded areas). Thanks for the reply Longhair......Al

You'll do well with that coil Al. The spokes on the 15" WOT MKII snag on brush and stubble a lot. It can be done (I have), but in ths case I think that less is more. That coil will hit hard enough on copper, and it will ring up high. How large, thick, and/or deep it is will have a bearing on just where it will ID.

Longhair.....When you say"where it will ID" are you saying that the size,thickness of object,how it's positioned in the soil will have an affect on the audio/TID? Pennies that I find(I'm a penny killer) normally ID at 28 to 32 but copper of varying size or thickness could have a larger range of ID? Am I reading you Right?

 

[Old Longhair]

Yep! The ID is based on coin size, shape, and distance fron the coil. This is why an iron nut that is an inch across and