Cooter & Thompy...Nugget Test Results

[Jim Hemmingway]

Chris....did the test today. Background info...ground balance at 84ish (scale 0-salt to 99-extreme, a reading of 75 upwards considered to be more magnetic susceptible conditions confirmed with a Fe3O4 reading of 0.1 to 0.3 expressed as % volume magnetite (a small magnet into loose soil for a few seconds, it comes up covered in iron "filings"). The soil had enough moisture in it to be "compactable", but not damp. Used max sensitivity in both the all-metal motion and in the JE disc mode, using the 7" by 11" DD coil (only coil I currently have).

The test nugget, maybe three or even four grains, measures about one-eighth by one-quarter inch in an oval shape.

Ground test results: (a) the all-metal motion mode gave a good solid signal at three inches, but the two-way signal was gone completely beyond three inches. (b) the JE disc mode gave a good solid repeatable coin type signal at three inches, but thats about it for depth. Quite a surprise, JE's strong signal.

Comment: In the JE mode, the nugget ID'd at a stable, repeatable 12 to 14 (iron disc range runs from 0 up to 15). The disc level could be run up just past "12" (small iron rejection) before the nugget was lost from detection at three inches; the sens decreased to "90" still gets a more modulated but repeatable signal.

Thompy: You may recall under the "metal detecting forum" that I had mentioned I would get back to you with some ground test results. Well, I finally cleared an area of roofing nails and got it done.

Jim.

[thompy]

nice write up Jim, soil conditions are close to mine, around here about 87, when i head up around the mines, i hit around 92-3 though it can change fast over short areas fe 304 .01 here up north Ive seen it hit .3, but usually forget to pay attention to it. last week i was up north and was detecting a lake, that the dam blew out on 4yrs ago, near the high mark was running 89 then the closer i got to the water i was down in the upper 70's , soil was moist but not saturated, the lowest readings i have seen on the t-2. there was a lot of dark flat rocks that ran around 40 which is the ferrous non ferrous break point, if the got to 3-4 in. thick they would read much higher, the surface looked like a mill scale was on them. meant to grab one to play with. must be some sort of iron, then the usual hot rocks. Ive read more stories of raw silver nuggets being found here than gold ones. thinking of hitting around a nother area near some more gold mines, these mines had a much softer rock, need to really learn the minerals in the area, some times i spend more time looking at the rocks than detecting

[El Cooter]

Give me a day, I am behind schedule.....



Coot

[Jim Hemmingway]

Chris: There is no hurry at all; when you get a chance, that'll be fine. Looking forward to hearing your test results.

Thompy: Sounds like your ground is a bit tougher than mine. Interesting with respect to your mineralized rocks. If your unit is similar to mine regarding the ground balance range, you might try checking suspect rocks in the all metal motion mode, with the ground balance set to "45". At that point, any non-conductive iron mineralized rock will cause my unit threshold to go quiet when the rock is brought up to the coil (bring it up and away briskly to avoid autotune cancelling of the signal as much as possible). You'll still get some overshoot response when you pull the mineralized rock away from the coil.

If the rock has sufficient metal in it to overcome the negative iron mineral response... it'll cause a positive response...you can be certain the rock has metal or conductive sulfide in it. You'll notice with this type of target, that as you pull it away from the coil, the signal immediately disappears. On the other hand, if the response is negative (goes quiet brought up to the coil), but the rock looks suspicious ie it's got quartz or a calcite material with a lot of iron staining (limonite for example), it's still worth checking out since any metal present may not give a strong enough positive response to overcome the iron mineral effect. I have found small "sponge" silver, and other disseminated silver fragments in such rocks that gave an overall fairly neutral response, when all visual signs indicated there ought to be a negative response. Something to keep in mind.

If you're not sure about your ground balance range compared to mine, email the question to DJ at Fisher. I originally guessed "40" for my unit, but was advised to stick with "45". Also, for unweathered rocks try using "65", as that setting offers less iron mineral bias against any positive metal signal that may be present in the rock.

Jim.

[thompy]

thanks for the responce, will have to try that when i get back up, suppose to go tomorrow, but think im going to hang around the house and hit an old park, family is heading up north for the mother inlaws Bday, plus i have some stuff to take care of around the house, i try this park mabey 2 a year , just so much trash, but it has been in use since the 1840's, and of coarse possible copper culture stuff

[El Cooter]

Okay Jim, did a little test. 2 grain irregular piece but flat. Ground 54, hard pack sandy type soil. Reads at 2.5 inches with target I.D. almost 4 inches total depth. running stock coil, gain at 8 and SAT at 7 which is how I run most of the time. This is a backyard test not actual Mother Lode type soil. I can do more tests if you wish...



Cooter

[Jim Hemmingway]

Chris... interesting to see how various units work in different mineralization. I know you are busy, so thanks for taking the time to run this test. I ran my MXT over the nugget at three inches; it barely responded. I'd never have noticed it had I not known it was there. But then, the ground here has fairly high mineralization. I appreciate your help Chris,

Jim.

[thompy]

Jim do you think the f-75 would hit it?

[Jim Hemmingway]

Hi Thompy,

A two grain flat shaped piece, I doubt it. To make that type of comparison, you have try ‘em side by side over the same target. I try to view these tests as a matter of interest only.

Jim.

[liquid1]

Good test folks..Jim do you feel like a small nugget in a creek bed will read in the 0-15 number range in the all metal or JE disc mode
I realize most of my local creek beds are sandy rocky conditions and might Detour the readings a bit..thanks james

[Jim Hemmingway]

July 6/08

Hi James,

Depends on the nugget size and ground minerals. In my ground a small piece of several grains ranges in the upper third iron ID area. Anywhere from 11 to 14 on the F-75. Larger pieces would read higher, how high depends on size, shape, profile presented to the coil, etc.

In highly mineralized ground non-ferrous targets can be skewed to the left of the scale (towards the iron side) to some degree. Your soil in NC might have this effect.

To get an idea, you might bury a few various size nuggets (if you've no gold, use lead nuggets made from fishing sinkers) into your ground at an inch or two, and see how your ID reacts. Use the All-Metal Motion mode for best ID stability, but also pay attention to the signal strength and clarity. Then switch over to the JE mode, and do a comparison with and without iron discrimination set up as high as "12" but no higher. At comparable depths, you'll find the JE mode will respond to the nugget with a crisper signal than all-metal motion mode, but will not surpass it in depth ability. Take the test a step further and bury small iron, and check it in JE with the disc set to "12". In my ground the iron is clearly disc'd out with at least a broken signal, while still clearly detecting a three to four grain nugget at three inches with a solid two-way "coin-like" repeatable signal. James, don't forget to ground balance beforehand, and consider going slightly positive on the GB up to, but no more than 3 digits max, but....only after you've first completed the test with neutral GB. You'll see that especially in All-Metal Motion mode, the signal on the nugget will be enhanced.

Jim.

[liquid1]

Thanks a heap jim..All I have here is fishing lead weights to campare and test with..It sure would be good to pull up the gold like cooter just posted..I'm leaning more toward the local creeks Being my best bet in these parts..awesome..