Nugget hunting with the F75

Has anyone here used their F75 to hunt gold nuggets with? If so what setting did you use.

Thanks,
Kirk

Well I tried. I was at Roaring Camp in early May. [www.roaringcampgold.com] Talk about iron masking. The ground was loaded with black sand. But after doing the ground balancing dance I tried sweeping the side of a cliff. This was an ancient tertiary stream bed. Oh wow was that cool! I saw a band of rust running through the cliff side which was pretty much pure black sand. ie., iron. To make a long story short. No beeps. Panning worked better.
I was set to DE mode, sens 70, disc 18. I dug anything that beeped. I found a rusty square headed bolt. Oooooo Ahhhh.

Kirk,

PM sent today.

Jim.

Thanks Jim!

Thanks for the detailed email Jim. I went on a group dig where we used a trommel to work the material. My plans were to use my F75 with the small coil to search the discards that came off of the machine. Ended up not even trying it out. Was too tired and spent my off shift sluicing and panning. Thanks again.

Hi Kirk...you're welcome, lets hope it will be useful sometime down the road. Its a pleasure to discuss F-75/prospecting applications, and good to learn there are a few other rockhunters (liquid1 is another) here on the forum. Good luck and HH.....Jim.

Hi NASA Tom...geez, I intended to answer back on Kirk earlier, but between this and that it almost slipped by. I prefer not to use the PM system, but my response was lengthy, and I had wondered if it might be more appropriate to PM it over to Kirk.

Lookout Tom, you may have to rethink the forum title to something like "inland coins, rocks, and relics". Interesting how you've attracted a number of us. The common denominator is that we all enjoy intelligent, straightforward discussion. All the very best to you Tom...

Jim.

Jim..... it is folks like you that add so much value to the concerted effort-of-discovery. Feel free to post lengthy dialogue.

Yes Jim..Please post your Knowledge away..Your Writings are like a great Mark twain novel!!!!
That keeps Folks glued to the Screen..Your Nugget Experiance Is Real World Time invested and Tested...As for me I am Always hunting that Big ole huge Gold nugget
....Thats somewhere Down on the Farm....James

Yes please post your nugget experiences. The kind of ground you might be hunting in might give me a clue as to how to setup up my F75 in my harsh areas.

Liquid/Mark/NASA Tom,

Tom, two more members have asked me to provide the PM information sent to Kirk earlier. I think perhaps that I was mistaken not to have posted it at that time. Please keep in mind that I am certainly no “expert” by any stretch, but rather…a hobbyist who enjoys searching for valuable “rocks” in natural environs while trying to improve search techniques. Sometimes it comes down to personal preferences. I stand to be corrected on any point, we all appreciate different perspectives/fresh ideas. The following text was sent to Kirk…

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I’ve been a bit reluctant to respond here because I have not used the F-75 for gold hunting yet. I have used this unit extensively for silver nugget/ore hunting here in Ontario. My preferable target size ranges from a half an oz to multi-lbs (different from tiny gold searching), but I also retrieved numerous pieces ranging from sub-gram upwards while getting acquainted prospecting with the F-75 last autumn. Due primarily to structure and mineral inclusions (lower conductive sulfides, non-conductive iron minerals) within the silver (in my area), most small silver target IDs in the lower foil range, some tiny pieces dipping down into the upper iron ranges when still in the ground…similar to small gold.

The 13 kHz operating frequency F-75 all-metal motion and JE discriminate modes offer good sens/depth response to large and small low conductives in both undisturbed and disturbed ground (for example, mine tailings, cultivated fields, loose material at the base of cliffs/slopes) using the stock 11” DD coil. For example, a freshly buried three to four grain (or so) flattish nugget at 3 inches and a real nickel composition pre-1981 Canada nickel @ 10 inches will both respond well in either mode in my mineralized soil (GB = 84ish, Fe3O4 readout = varies between 0.1% and 0.3% volume expressed as magnetite) using the stock coil. In fact, using the stock 11” DD coil only, the JE mode even with small iron discrimination settings, will yield a “crisper” response to either target, although no deeper than all-metal motion mode on the small nugget.

Sensitivity to nuggets at a few grains and especially sub-grain size improves by using the smaller 6” concentric elliptical coil. The stock 11” DD coil will signal in the air to about half an inch on approximately half-to-two thirds (an estimate) grain flattish nugget. With the 6” elliptical coil, a repeatable signal at two inches can be had in all-metal motion mode, while JE disc mode with “0” discrimination will signal at two and a half inches. The improved JE mode result may be due to the all-metal motion mode’s fast threshold retune rate tendency to “tune-out” tiny nuggets a bit, but that’s a guess. I have not buried and depth tested this sub-grain nugget yet, so no ground results are available for it.

Although all-metal motion mode air depth results are similar to the 11” DD on the three to four grain nugget, the 6” elliptical coil outperforms the 11” DD over this nugget in the ground with a noticeably stronger signal response. This coil has impressive (although reduced compared to the 11” DD stock coil) depth response to larger targets despite its size.

I don’t own the 10” concentric elliptical or the 5” DD coil and cannot comment on their capability.

The JE disc mode with stock 11” DD coil, and using small iron discrimination is a good combination for locating desirable targets at several grains and larger in iron trashy tailings with very little sensitivity loss by contrast to using the all-metal motion mode. By comparison, the motion all-metal mode’s adjustable threshold, fixed but fast threshold retune rate, and good sensitivity to small low conductives make it a good choice for searching natural environs with either coil. Visual target ID is available in this mode to help with identifying small iron trash.

The F-75’s manually adjustable, calibrated ground balance scale allows the operator to run the unit precisely with either a positive (to enhance signal strength on fringe depth targets) or negative GB offset (to soften or eliminate positive hot rocks where possible/necessary). More, a GB setting of “45” can be used in a bench test to distinguish positive responding low conductives from non-conductive iron mineral hot rocks by their negative response. This is not a foolproof method, since some tiny gold response can be smothered by a negative, non-conductive iron mineral response. More on this technique in the field will follow.

To compliment the manual calibrated ground balance, a highly sensitive stat (non-motion) all-metal mode is available and absolutely essential to properly perform ore and mineralized rock bench tests mentioned in the preceding paragraph. Note: I might have also added here that the all-metal motion mode while convenient in the field, is not the preferred choice for bench testing suspect rocks, as the retune rate will significantly reduce the sensitivity to tiny amounts of precious metals/sulfides.

The F-75, similar to GMT, features the Fe3O4 bar graph readout. This readout, expressed as % volume magnetite, should be viewed as a measurement of magnetic susceptibility that results from any ground mineralization present. It is most affected by the presence of magnetite and to a lesser degree, maghemite. It is an easy to use, effective tool for locating black sand deposits, and therefore gold/precious metal values if present.

By comparison, the ground phase as represented by the calibrated GB scale…should be viewed as a ground "target" measurement (based on phase shift) that generally indicates “type” of ground mineral. This is not exact science as varying mineral types and amounts present in any given soil can give similar ground phase readouts. Regardless, the operator must ensure the unit is consistently kept balanced to the ground…whatever the readout. This is particularly important when over higher mineral ground that is less tolerant of improper GB settings than is the case with lower mineralization levels.

Generally, VLF units are highly useful for sampling sites suspected of containing precious metal values in the form of small nuggets at least. Keep in mind that as ground mineral magnetic susceptibility increases (particularly due to two primary substances…magnetite and maghemite), the depth/sens performance will decrease accordingly.

Due to its modest prospecting operating frequency but high sensitivity, the F-75 is an excellent choice as a prospecting unit. It will nip at the heels of higher frequency units over tiny nuggets (a condition that is dramatically improved on sub-grain nuggets by using the small elliptical coil), but will suffer less depth/sens loss in higher magnetic susceptible ground compared to the higher frequency units. To reiterate, the all-metal mode’s fast threshold retune rate, target ID for iron trash/hot rocks, good stability even in higher sens settings generally, make this mode well suited for gold hunting.

Summarizing, use the all-metal motion mode where feasible in low trash/hotrock environs. A barely heard threshold hum, highest sens possible without undue falsing/instability, and use the target ID for hot rock/iron identification. In my area hotrocks will normally ID “14”. Experience will dictate for your area/hotrock type. More, you may elect to use the more time consuming method of using ground balance adjustment to the “45” setting for hotrock ID as outlined below.

In trashy/excessive hotrock environs while employing the stock 11” DD coil, use the JE mode with small iron discrimination. That means an iron disc setting of “12” in this mode. The other disc modes normally run small iron disc at a setting of “6”, but this does not apply to JE mode. I recommend one of two methods for hotrock ID, (a) use the target ID or (b) retrieve the target and flip over to all-metal motion mode and adjust the GB to a setting of 45. In this motion all-metal mode and GB45 setting, any positive hot rock that formerly gave a “zip zip” signal will now give a “boing” signal. You may elect to use the more sensitive stat all-metal mode with the “45” GB setting, whereby any hotrock will go silent when the coil is passed over it. If the target still responds with a positive signal, you’ve located either a low conductive sulfide or a native precious metal (gold).

The above “GB45” hotrock “check” method will at times entail loss of some tiny targets within a rock structure due to their signal response being “smothered” by negative iron mineral response. Using target ID for hot rocks will also mean missing occasional small gold that may read similarly. Keep in mind most hot rocks lose their signal strength very quickly compared to metal targets.

Use highest sens possible in JE mode similar to all-metal motion mode, single tone only, again…disc set to 12. If hotrocks are a real time consuming distraction, you may bump up the disc to “14” to simply eliminate them. Again this will mean losing tiny gold, especially fringe detection targets, but that is the price paid for the convenience of hotrock free searching. In such areas the alternative is to use a suitable PI unit.

When using the small elliptical coil, do not use discrimination in the JE mode unless you are willing to sacrifice small gold. Best to stick with the all-metal motion mode when using this coil, especially over the higher magnetic susceptible minerals normally found in gold country.

The only way to get it all is to dig it all…which is my tendency…but then I recognize the positive hotrocks in my area by sight generally. When using a VLF unit, the best option is to learn to identify hotrocks by sight, they are usually on the surface or very near to it. Most serious prospectors employ suitable VLF and PI units in gold/silver country, using each where best suited/applicable, in accordance with ground mineral magnetic susceptibility, hotrock prevalence, small iron trash abundance, and most important…the size of gold anticipated at any given site.

I hope this will be helpful to you. Remember to be persistent, and enjoy the great outdoors. Good luck and HH…

Jim.

PS: I might have added to Kirk that I do not recommend the use of tones, but rather, use only single tone. The use of iron tone will certainly mean losing even large nuggets at depths beyond six inches or so in disturbed ground (ie mine tailings) or loose mixed till substrates. Perfectly good targets will yield a good signal but read as iron and therefore be included in the iron tone.

Now, with the stock 11” DD coil using small iron discrimination and single tone, the operator will be alerted without iron tone bias to those potentially desirable targets in “disturbed ground”. This set-up, despite IDing these targets as iron, will not discriminate them out at the “12” setting, but will discriminate small iron. At least in any higher mineralized soils with which I have experience.

More, in undisturbed ground in the presence of either hot rocks or iron trash nearby, again, iron tone usage will mean losing good targets. The combined reading in such scenarios may very well result in an iron ID, thus using iron tones will cause the operator to ignore such signals.

In summary, when using JE discrimination for prospecting, do not use tone ID.



Edited 1 time(s). Last edit at 08/03/2009 11:29PM by HumblePie.

Thanks a Big heap jim....For posting.....Here ...I am sure lots of folks will get good use from your info..Has Tom Actually seen your Findings From the Great White North..Simply Amazing..We Down here can only hope to find a ring size nugget Down here. James

Thanks for the info

Hi Mark/Liquid/Kirk,

Was out in the garden thinking about the above post oddly enough. I got to wondering if a rationale might be useful as to why I recommend a small iron discrimination of "12" while using JE mode for prospecting.

Yes, lower disc #'s will eliminate/break-up various small iron pieces no doubt. A disc setting of "12" is the highest "safe" iron disc setting that should be used while not noticeably degrading the signal on low conductive ores or small nuggets of a few grains...and this especially applies to any desirable targets found in disturbed ground, for example...mine tailings, loose unconsolidated material, material that accumulates at the base of slopes and even cultivated fields. A setting of "13" usually is OK but a bit iffy, at "14" the signals on small nuggets/low conductive ores begin to degrade, "15" is undependable as such signals can disappear entirely.

Try burying some real nickel content nickels at various depths and check the signals in JE mode up to a setting of 12 or even 13ish. Now try the other disc modes with any discrimination dialed-in. At least in my soils, any discrimination dialed-in with DE/PF/BC modes results in quite a large depth reduction in terms of good repeatable "diggable" signals.

Jim.

I'll try those ideas. Any edge is an advantage. I tried the je mode last night with the 12 discrimination and was surprised how quite the machine ran.

Hi Mark,

Depending on the EMI levels in any given location, yes the "12" disc setting makes a difference in stability and quieter operation. If hunting in undisturbed ground where foil elimination is desirable (personal preference) the unit's stability will increase substantially. As discussed on our PM exchange today, fortunately the benefits of JE mode are mostly applicable to areas (prospecting environs,and cultivated fields for example) more removed from high EMI sources.

EMI can/does fluctuate considerably seasonally, and diurnally in urban areas. Summertime evenings here in the neighbourhood, especially weekend evenings JE mode in my area is mostly not useable above very modest sens settings. Later in the season when air conditioning and pool pumps etc are turned off, I frequently can use JE mode near or at max sens settings.

That said, unless there is a specific reason, for example disturbed ground resulting from urban renewal projects, my view is that there is no advantage to be gained using this mode in undisturbed ground. It's too finicky/subject to EMI and sensitive to every little tidbit of conductive material. More, I see no measurable difference in depth/sens capability over the PF/DE disc modes for coin hunting in undisturbed ground.

Jim.

In my experiences...... field and/or bench-testing .... (as long as EMI is near zero)..... the JE mode is a tremendous boost in Sens to tiny (not micro) low conductors. When the targets are of Trime or Half Dime size (or larger)........ the JE mode is of no benefit....... no additional boost in depth performance between JE vs. PF/DE modes.

Figured I better get around to joining this Forum since the discussion is turning to the F75 and nugget hunting. I have used the F75 for nugget hunting since it first came out. But since I only get out occassionally I do not post much and I do not keep in practice so I am always a "beginner" with the F75.

I am going to re-read the responses as I am sure I will find some new techniques. (Thanks!) I had suscess in Alaska with the F75 and I have been out recently in detected areas. I found snmall gold with the small coil. I keep it simple, just use either JE or all meteal (depending on which seems to work best for the ground), little or no discrimination, one tone, and I keep a check on the mineralization and hot rocks. Upon reading these posts I want to now take some time to play around with hot rock masking, the amount of mineralization, and discrimination. For a beginner just keep it simple. That is all the F75 needs to find gold!

Hi SRLance,

Welcome to the forum, its great to have another "rock" hunter aboard. I agree with you, its a good idea to keep it simple when operating the F-75. NASA Tom has an acronym for this philosophy..."KISS"..."Keep It Simple Stupid" and at times some of us analytical types can benefit from keeping this in mind.

Please don't hesitate to post your nugget hunting experiences, techniques or questions wrt the F-75, we'd enjoy some fresh input on this subject. And don't be afraid to forward your ideas even if they seem a bit questionable. This is a family oriented, very friendly forum where NASA Tom provides excellent technical guidance. One result is that we do tend to leave our "fishing" rulers behind when posting here.

Look forward to hearing more from you SRLance...

Jim.

Thanks Jim - I hunt in N. Calif and here we have a lot of water action. Almost all of my gold has been found in close proximity to bedrock and/or in tailings were the deepest material from the creek or river is now on or close to the top. It does take knowledge of where and how to look in combination with the F75 to get gold and then have a lot of patience. I have often gone some days without a speck to show. My largest, in many years of looking, was over an oz. I just got a New 49er's membership and I hope to put the F75 to work on some of their claims along the Klamath River in a few weeks. If I find any nuggets of decent size I will be sure to post.

Hi SRLance,

I'm over here in Ontario where I've searched for silver ores/nuggets for some 24 years. Usually for a week or so in the autumn until I recently took early retirement. Now, September/October are devoted to this pursuit.

Silver is not gold in terms of bullion value, but two factors help alleviate that condition..(a) the silver can be found commonly in multi-oz up to multiple lbs, and (b) the specimen value for "character" pieces tends to significantly offset the bullion value aspect. Mind, I don't sell my finds, therefore this is not a primary motivating factor. I enjoy the wilderness environs and making a few finds along the way. If those finds happen to be of good value, that adds a little more "fun" factor to the experience.

Speaking of experience, I've been learning some pretty basic things lately. I finally bought some high quality headphones...something most of the experienced men here probably take for granted...the "NuggetBuster NDT" phones, and these headphones really make the F-75's audio "come alive". I'll never hunt without them again. Live and learn.

I've found the F-75 in remote/rural areas to be very quiet/stable using JE mode and stock 11" DD coil, with sens near maximum. Its a pleasure to be able to utilize the full deepseeking power of this unit on small low conductives while still invoking small iron discrimination under minimal or practically non-existent EMI condtions...when searching mine tailings. More, the smaller 6" elliptical coil certainly helps this result where some EMI exists in these areas. Have your experiences been similar in your area? Later,

Jim.

I do not seem to have a problem with EMI - perhaps the hot rock noise here cover over any EMI from nearby powerlines. I know with too high a sensitivity that I could be loseing targets due to masking. In an area with larger nuggets, I think turning the sensitivity down to 50-60 would not lose that much depth on large size targets.

For finding gold, except for the larger nuggets, it is just the thrill of the experience of first seeing that nugget in the dirt. I just do not put monetary value on most of the gold I have found. For me it would be an equal experience to find silver nuggets.

Hi SRLance,

I apologize for not replying sooner. The wife and I have been packing the camper for a trip north so we've been busy..so many little things to think about. There's a number of topics I'd enjoy discussing with you regarding your gold hunting in California, but I think it'll have to wait for another time.

For example, I've been wondering what influenced your decision to go with the F-75 as opposed to one of a number of more traditional VLF prospecting units. I know that I felt the F-75 was an all around more capable/desirable unit, despite not being quite as sensitive to the tiniest pieces as say, a GBII unit. By way of equalizing that condition, I felt for example, the F-75 would perform better over higher magnetic susceptible ground, and would do better generally on larger targets to better depth. A reasonable view. And, the F-75 is far from being a slouch under any circumstances.

Another question that came to mind, was the cost of the membership with the 49ers, and how long is it active? But as noted, these topics can wait for later.

I agree with you about loss of good targets when sens is set too high over tough ground mineral. The "high beams in fog" scenario. I've wondered which mode you prefer in tough ground when EMI is not a factor. Where EMI is a factor, I've found the all-metal motion mode to be far more preferable to use, and use at considerably higher sens settings than would be possible with the JE mode (even using small iron disc). I enjoy using all-metal motion mode in quiet (more trash free) areas, but it's personal preference as much as any other factor.

Finally, I agree wholeheartedly with your philosophy regarding prospecting, regardless of whether its silver or gold or whatever. I know some hobbyists enjoy searching for native copper nuggets on Michigans Upper Peninsula. Its almost ironic that one such piece of a few lbs... with attached chlorite crytals recently sold at a mineral auction locally here for an astounding sum. I won't give the figure, its hardly creditible. That said, I'll be gold hunting the early part of this autumn, it'll be an interesting change since it will also include significant streamwork.

All the very best with your Klamath River searching, please do return here with your findings and any questions. We rock hunters can learn from each others' experiences and insights. I'll definitely keep an eye out later on in the season for anything you might post. Take care and HH,

Jim.

SRlance, Great to see ya on Here..Its not every Day We see a Detector that hunts for Gold/Silver Nuggets..Jim Is an Exception To the rule..Best Put.. His Experiance and Knowledge Is Amazing to the Cause....
I live here in Nc Near a Huge Gold Rush County and Always Look For signs In Creek Beds, and Hit the creeks with every chance..I have Access to 200acres and it has a creek running trough it and gold has been found There..Also It has Civil War And settlement History..My problem is Time Is not on my Side...
My F75 settings are Usually In the Je,All metal,And Stat mode When hunting Gold creek beds..11" and 6" coils..I love Walking the Creeks..
Jim has Given me Great Advice for What to look for Any info you can Offer will Be greatly Appreciated..Good luck and keep us Posted..james..

In response to HumblePie & liquid 1 (Which I assume refers to water, of course) I got the F75 because of its light weight and all around sensitivity. I took the arm rest off which I do not need for the small coils and put some tennis wrap on. Thus the F75 is one of the lightest of the detectors and is great when I am also hunting those creek beds. For the larger stock coil one could put the arm rest back on or do as I have which is to use a bungie cord connected with "liquid weld" to the tip of the stock coil and then also back to the other end at the battery housing to prevent the unit from falling when I kneel.

I usually prefer the all metal, but in some ground the JE mode could be better - just have to try both modes. I will keep you posted on how I do on the Klamath. For the gold dredgers I am sure hoping our Governor vetoes that SB670. I will PM on 49er membership.

Thanks Lance, I just got back from a wet, cold, abbreviated camping trip. Nothing but pouring rain. I have returned your PM tonight, again with sincere thanks for the further information. BTW, I cut slots and added velcro straps to my armrest, but need to do something similar to ensure the unit stays reasonably dry while doing streamwork. Later,

Jim.

Hello Jim.
The more I peruse this forum the more aware I become of my ignorance regarding detecting. I had not idea.
Unfortunately this defines my inability to understand much that is shared by members like yourself and Tom. However, one thing is clear, this is the right place to start.
Since our resident guru Tom, bowed to you regarding my quest, please accept my gratitude in advance for any thoughts that might come to mind.
I mine placer gold in northern BC, just south of the Yukon border.

My first intention is to determine what detector might be suitable to start with for outlining pay-streaks on ground which is being stripped with dozer or excavator. The depth of layer removed could be tailored to whatever depth the detector achieves, hoping for one foot deep increments minimum. The target is gold in two size distributions; the first will have its margins flagged for bulk processing, >0.1 to 1.5 gram; the second: >5/8" which would otherwise pass over mr.screener and onto the tailings dump will be hand picked. Much magnetite is present, with and without gold.

My second endeavor, since prospecting is infinitely more enjoyable than mining, is tracking surface veins of quartz which can contain >0.25 oz chunks of gold. These veins often exhibit large rusty zones near enrichment, and contain many chips of scrap iron, drill steel, pick-ends and timber-spikes. Fortunately the miners of yesteryear didn't have pull-tabs on their beverages.

Remember, "think yellow" and "dream big".
Tim



Edited 1 time(s). Last edit at 05/09/2016 06:03AM by bcgoldminer.

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Edited 1 time(s). Last edit at 05/09/2016 06:19AM by bcgoldminer.

Tim....... good job finding this! And Jim lives in Canada also. I don't know how often he frequents this forum....... but I do believe it is on his list.

Hi Tom.
Thanks again for your great Forum and the medium is provides.
There's gold, and it's haunting and haunting;: It's luring me on as of old;; Yet it isn't the gold that I'm wanting: So much as just finding the gold. .... Robert Service.

With this, I think prospectors and treasure hunters alike can identify with something we share in common.

If Jim doesn't reply too soon, and my bit wears out, I'll track him down one way or another.

Tim

If I remember correctly Jim posts here as Humblepie but he has been absent from the forums awhile now - no doubt out prospecting. Hopefully he is finding lots of silver!

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