Why is Important to Keep a Logbook when Prospecting with a Metal Detector

A logbook is a formal written summary of gold prospecting trips. A logbook doesn't have to be extensive, however, important details must be accurately recorded. In my logbooks I usually record the date, the location, such as the GPS coordinates or general location, equipment used, metal detector settings, or other pertinent information about a place. A logbook can also be used to record useful information such as when you submit an assessment report like expenditures: gasoline, equipment rented, time worked, etc. As an example, I thought I would share with you some random records:

"Jolly Creek - old working 11U34xxxx 54xxxxx. Just got there and I've seen that someone dug a hole, so I checked it out. Found a nice 0.5grains gold flake. Equipment: GB2 w/ 6" coil, Gray Ghost Original headphones, sensitivity 6-7, ground balance around 8, mineralization normal, audio boost, on bedrock. Old working, a lot of whiskers from old metal brushes used to clean-up bedrock, very hard to spot. My nugget gave me a very distinct whisper, not the screaming sound the metal wire used to gave me. Notes: the others guys digging gave me an indication where to start! (August 16, 2011)"

"August 8, 2012 - Rock Creek at the mouth. Checked old hydraulic. GB2 w/ Ghost Original, 6" coil, mode normal, mineralization normal, ground balance ~8, sensitivity <5. Found a lot of iron nails, still more to check in the area. I think it has potential."

"August 31, 2016 - Yalakom River, TDI Pro w/12" DD.  GB @ 8/7, sensitivity 2-3, pulse delay 10μS. Too many signals in the camp, moved by water & found 30-30 cases, lead bullets, and bullets’ copper jackets. Found a case of beer about 10" deep."

As you can see, the information recorded doesn't have to be extensive. It’s also nice to read them in the winter and plan for the next year.

Happy hunting,

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Metal Detecting Tips - Prospecting for Placer and Epithermal Gold

In this blog you'll find a few tips and tricks I've learned over the years when searching for gold with a metal detector using a Fisher Gold Bug 2 (original model) and a White's TDI Pro. Obviously, most of the controls are the same or similar on other models, and different manufacturers may use different names for controls that do the same things. If you have questions send me an email by clicking the name bellow.

Happy hunting,

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Ground Balance

• always set it a little positive (louder going down), never negative

• adjustment of ground balance becomes more critical as the ground becomes "hotter"

• before you start digging, check the ground balance one more time; it will save you a lot of work

• you can set the ground balance to the "hot" rocks, but sensitivity will become lower

• a good target can never be "opt-out"

• check ground balance every 10 feet or less

• always ground balance to the general matrix of the ground

• try different spots to check the accuracy of the ground balance

• if the soil is not mineralized, just set the ground balance to the middle (or turn it off for PI or Pulse Induction metal detectors)

 Sensitivity

• always try to use it wide open and have audio boost on

• try the settings with the test piece

• set the sensitivity down if the soil is too mineralized

• make a test piece

• beginners should try lower sensitivity, as there will be less chatter

• in iron discrimination mode, a higher sensitivity will make the machine have a higher pitch

 Mineralization

• if we have to turn the gain setting down bellow 2-3, turn the mineralization setting to high (Gold Bug 2 only)

• check with a test nugget between .5 to 3-4 grains depending on how bad the ground is

 Threshold

• the lower the tone, the more sensitive it is

• set the volume to maximum, so you can lower the threshold

• this setting can have an effect on the "iron discrimination" setting

• the tone drifts with temperature, so it needs adjustment from time to time

• set the sensitivity in such a way that the threshold doesn't chatter

• if there are a lot of "cold" stones around, try to ground balance using them; sometimes the most you can get is double-beep, and other times they can be tuned out completely

Volume

• keep it high enough that it doesn't hurt you when you sweep over a can or your car

Iron discrimination (GB 2)

• sensitivity and depth are reduced

• knocks out virtually all hot rocks

• if you get a good signal for "hot" rocks of small size, crack them open, they may have gold or platinum inside

• it is important need to learn how weak a signal can be in "normal" mode and still be able to hear it in "iron discrimination" mode

General tips

Remember to always use a test piece to check your detector's settings. A test piece is a small nugget (I use multiple test pieces with gold size between 0.5 grain to 1 gram) glued to a brightly colored plastic card. Just throw the card on the ground after you ground balance and set up your detector, and tweak the controls and adjust the height and the coil sweep speep until you hear the most clear or distinct sound.

Bedrock

• check the bedrock even if there are no visible cracks

• purple stains with adhering clay indicate hidden crevices and gold

• any cemented material should be crushed and panned

• sometimes the crumbled stuff is the weathered bedrock

Old workings

• if you find boulders piled up, move them, as underneath them can be a rich mineral patch

• scrape the dirt over the bedrock to expose it

• in gravel which may contain nuggets, use a scrapper to bring up the dipper material

• check the bedrock even if it is vertical

Detecting

• after you have dug up a target, check the spot again; nuggets are sometimes found in clusters

• keep the coil as low to the ground as possible

• grid the nugget patch

• rake the surface

Stick or no Stick Field Weld Repair

Mining equipment makes use of a wide range of materials, from "ordinary" steel, to manganese and austenitic stainless steel. In this series of articles I will try to help new mining equipment operators who have taken on the task of repairing their own machines.

Stick and Mig welding

Most people use stick (SMAW) and mig (GMAW) as their primary method of welding. Even though these methods are more or less adequate for small jobs, there are better alternatives available.

Flux-core welding

FCAW or Flux-Core Arc Welding uses tubular electrodes. One of the most common and versatile electrodes is E71T-11. This electrode is offered by many suppliers and comes in diameters from 0.030" or 0.8mm to 5/64" or 2.0mm. Its voltage and amperage range from 14V and 25A to 22V and 315A. This electrode is self shielded, in other words it doesn't need shielding gas and can be used, within reason, on contaminated materials. This wire can be used in all welding positions. Another versatile electrode and a favorite of mine is the one offered by Lincoln Electric, Innershield® NR®-212. Offered in diameters ranging from 0.045" or 1.2mm to 5/64" or 2.0mm, this electrode is great for a wide range of materials, from low grade steel to lower grades Hardox^® and AR (abrasive resistant) plates. As with any other flux-core wire, it is smoky, but that’s not a big problem if you’re outdoors and when combined with a respirator.

Always weld stringer beads, never weave beads regardless of the welding technique.

In a future article I will talk about steel grades and what electrodes to use depending on the application and material. If you have questions or suggestions regarding future articles, you can contact the author by clicking on the name at the bottom of the page.

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Materials used in mining equipment

Mining equipment makes use of a wide range of materials, from carbon steel, to manganese and austenitic stainless steel. In this article I will try to help new mining equipment operators understand what and when to use them as well as tips on welding.

Austenitic stainless steel

300 series stainless steels are classified as austenitic. They are hardenable only by cold working methods. These grades have chromium 18 up to 30% and nickel 6 up to 20% among other alloying additions, like manganese. Type 304 is the most widely used alloy of all stainless steels. 300 series stainless steel alloys resist corrosion, maintain their strength at high temperatures and are easy to weld.

Welding 300 series stainless steel

For stainless steel types 301, 302, 304L, 321, CF-3, and CF-8, use E308 electrode.

For stainless steel types 304, 304L, 309, 309L (often used in welding stainless steel to carbon, low-alloy, heat-resistant and clad steels), use E309 electrode.

For joining 316, 316L, CF-3 and CF-8 stainless steels; molybdenum is added to help prevent pitting and increase creep resistance use E316 electrode.

Depending on the application and/or thickness, flux-core electrodes may be better suited for welding 300 grade stainless steel. I’ve had a great experience using BLUESHIELD 652P-316L Stainless Steel Flux-Cored Wire (FCAW) in 0.045" diameter. It’s as easy to weld as E71T-1 and the slag peels off easy. Obviously, solid wire and stick wires can be used as well, with the disadvantages mentioned in a previous blog (see part 1 - "Stick or no stick").

Manganese steel

Manganese steel, sometimes called Hadfield steel, is a grade of low alloy steel used in high impact applications, like mining equipment hammers, crushers and jaws. Many people wrongly assume abrasive resistant steel like Hardox^® or other grades can be used to replace it. A client of mine used to replace the jaws on his excavator jaws crusher accessory with abrasive resistant material. After a lengthy talk, he agreed to allow me to build-up the teeth using manganese steel electrodes; suffice it to say, my client only needed another built 2 years later; think of the money savings and the low equipment downturn. Manganese steel is self hardening, that make machining and even grinding difficult. Although oxyacetylene can be used for cutting in the field, the preferred method is plasma cutting. Shops can also use water-jet cutting and laser.

Welding manganese steel

Welding manganese steel require special grade wire or sticks. A wire I have used for years and one that I’ve had great success with is Hobart TubeAlloy^® AP-O. It’s hard to source these days, but this wire can be successfully used in the field using a somewhat more powerful welding machine that can use 1/16" wire. This wire can be used to build-up manganese steel, join carbon steel to manganese steel, or weld manganese steel parts. Use a respirator, as this wire has a high content of manganese and chromium. As with most hard-facing overlay, this wire can be used in horizontal and flat positions only. Keep the inter-pass temperature low and you should be fine (manganese steel becomes brittle if allowed to heat-up too much).

Abrasive resistant steel

Abrasive resistant steel or AR, not to be confused with manganese steel, is a low alloy steel. The common AR grades are 400 and 450. These grades are relatively easy to weld following some basic rules. First, the choice of electrodes. Below is the electrode classification as recommended by SSAB in their Welding Handbook (copies are available for download on their website). Although recommended, I have never had an instance in which I had to use flux-core higher strength E8XT-X for any weld repairs or for manufacturing new equipment.

Second, control the heat input and the inter-pass temperatures. For single plate Hardox^® 400 20mm and Hardox^® 450 25mm, the material temperature should be at 20°C. Preheat as necessary.

Always weld stringer beads, never weave beads regardless of the welding technique.

In a future article I will talk about steel grades and what electrodes to use depending on the application and material. If you have questions or suggestions regarding future articles, you can contact the author by clicking on the name below.

This email address is being protected from spambots. You need JavaScript enabled to view it.