White's Pulsescan TDI at Moore Creek, Alaska

[steve herschbach]

I run a "pay-to-mine" operation at my gold mine at Moore Creek, Alaska. The location has mixed hot rocks that severely impede the performance of regular metal detectors. I was very excited when White's announced a new ground balancing pulse induction detector, the Pulsescan TDI, because I figured it would do well at our mine. As part of the operation we want to provide detectors for our visitors that do not have their own.

These people by nature have little or no detecting experience. I was happy to find some stock settings for the TDI that worked well at Moore Creek. I could basically set the detector for somebody and as long as they did not touch the controls it worked well. Just turn the detector on and go.

Still, experience counts for much and novices have a tough time finding gold nuggets, just due to lack of basic detecting skills. We have found in the past that regardless of the detector used we are happy if novices can just find any gold at all metal detecting during their visit. So I was very pleased that half a dozen new detectorists found their very first nuggets metal detecting with the White's Pulsescan TDI. The unit is not only very capable but also quite easy to operate and so really the only task left to the novices was to get over a nugget.

Mike B & Karl E of Anchorage with TDI Finds

Close-up of Mike and Karl's Gold

Moore Creek visitor Pete W from Paducah, Kentucky. Pete hunted hard with the Pulsescan TDI but was having little luck. I was out with him at one point and was sitting nearby when he got a signal. He started to dig with his scoop but the target was deep, and so I cam over with my pick to help. I scooped a pretty deep hole, but when he checked the target was still in the ground. So I dug some more and out popped a really good looking nugget! A very nice piece weighing .27 ounce that put a huge smile on Pete's face.

Close-up of Pete's Nugget

Moore Creek visitor Jens S from Hupstedt, Germany with nuggets he found with the White's Pulsescan TDI. The larger nugget is .62 ounce and the smaller .37 ounce. Jens found the smaller nugget first within ten minutes of turning the TDI on for the first time.

I was doing some bulldozing at our gold mine at Moore Creek, Alaska to stir up some nuggets for our visitors. I got to one little knob of gravel and after I flattened it out I thought "that looks like a good spot". I had not done any detecting in a couple weeks and figured it was about time. So when I got the dozer back to camp I got the White's Pulsescan TDI out and headed to the location. A guy had just come into camp as I was leaving and so I told him to head up the same way.

I got to the spot and started detecting. First down one row and up the other. After about ten minutes I got a nice signal, and dug up a great .31 ounce specimen. It is a little section of a quartz vein with a nearly solid gold core of gold running through the middle.

I turned off the detector and headed back to camp. The other guy was now just arriving and asked me what was wrong. I told him nothing was wrong, but that I'd got my nugget and so was done. You should have seen the look on his face! Poor guy had been looking for gold for days and I walk right out and find a nugget in ten minutes.

We had an 82 year old gentleman in camp that week who was not having much luck detecting so I gave the specimen to him to take home to Florida.

So what were the settings, etc.? I did not get fancy. Pulse Delay 10, Gain 12. The GB was tight as we have both a positive and negative hot rock at Moore Creek. A bit one way and the positive rocks signaled and a bit the other way and the negative rocks signaled. Negative hot rocks are by far the more prevalent. In general a setting between 9-10 eliminated nearly all the hot rocks.

However, late in the game I determined a couple things. First, virtually all gold at Moore Creek gives a high tone, even multi-ounce pieces. I believe this is because of the generally high silver content combined with the specimen nature of the gold. You can figure with 99% certainty that a low tone is an iron target or hot rock at Moore Creek. Next season I plan on having the novices run the unit in low conductive mode only to eliminate most large iron and any possibility of the negative rocks sounding off.

I ran the new 7.5" coil a bit and found a 1 pennyweight nugget with it. I was surprised at how stable the smaller coil was, as I expected it would be more prone to hitting hot rocks, but instead it seemed to be more immune to the hot rocks than the larger coil.

We had three days of pouring rain and although a couple other detectors temporarily failed all the TDI units came through with flying colors. I plan on returning to the mine August 8th for a week of detecting with friends and with the pressure off I'll have more time to detect myself. Between now and then I hope to get some good wading time in with the unit plus go chase more old coins.

Sincerely,

Steve Herschbach
Moore Creek Mining LLC
website www.moorecreek.com

 

[Eric Foster]

Hi Steve,

It would be interesting to see at what size nugget the audio changes to a low tone. Do you have any larger solid specimens that you can test? When you quote the weight of a specimen nugget, I presume that also includes the rock?

Eric.

 

[steve herschbach]

Hi Eric,

Well, I no longer think size has much to do with it. From the thread at http://tdi.invisionplus.net/?mforum=tdi&showtopic=97

"Hi All,

Reg, that was an excellent post on explanation of the conductivity toggle. I would like to add a bit more information that I discovered just recently. In testing all of the gold nuggets I had I noted that most all sizes up to a 12 oz quartz specimen containing 3.5 oz (by spec.gravity) registered as Low Conductive as I would expect , However, I had one piece of about 4 DWT that registered High Conductive. I thought it might be contaminated with iron or whatever. But in questioning Eric I found that gold when very pure will read High Conductive rather than Low and that impurities or alloying gold will drop the conductivity to Low. So I started to test many samples of gold and was really surprised. All my gold bullion, such as Canadian Maple Leaf and Chines Panda, which are pure gold registered High C. $5 to $20 US gold coins registered High Conductive. They are 90% gold content. the $2.5 gold coin registered Low Conductive. I then had a friend who has Australian Gold nuggets and all of his samples small and large registered as High Conductive. Remember, that all but one of my US gold nuggets registered Low conductive. So purity of the gold actually made a difference. So my one specimen was actually not contaminated but actually more pure than the rest. The gold here in Cal,Nev and AZ is around 80-85 % or so gold. I am sure some even less and is alloyed with Silver, copper, Platinum etc. This sure was an eyeopener. I am sure size and shape has a bearing as well. We also have some very crundgy gold which is invisible to our unit as well as to the Minelab SDs. It is very porous and appears to have holes throughout.

Again, Thanks Reg for the good iinformation. Jimmy Sierra"

followed by this reply from Reg:

"Hi Jimmy,

You are right about this gold reading as an eye opener. Thanks for the information about the gold coins also. I was wondering about how they would read.

When Steve Herschbach mentioned all of the nuggets he tested read as low conductive targets, even the larger multi oz ones, I really got to wondering why. This didn't jive with my testing of the nuggets I have left. Most of what I have left are ones found at Rich Hill and most of those read as high conductive targets if bigger than 1/4 oz. I did have 3 large nuggets from another area that did respond as low conductive targets and I just assumed the reason to be because they were very coarse.

Anyway because of what Steve mentioned, I started searching the web for info about gold and the conductivity of it when alloyed with other metals. I was really surprised that I couldn't find much information at all. However, I did run into a couple of key sites, one on gold alloys and the other on conductivity of metals in general.

Here are a couple of links;

http://www.kp44.org/ftp/ElectricalConducti...OfMaterials.php

http://www.deringerney.com/materials/GoldandGoldAlloys.asp

Now, when you look at the two links and sort of compare them something important stands out about gold. First, pure gold is a very high conductive metal. However, it doesn't take too much silver or other alloy metal to make that high conductive metal a low conductive metal.

Remember, the key when looking at the two sites is to look at the conductivity numbers. Pure gold is generally 70 to 77 on a conductivity chart but mix some silver with it and it drops to as low as 10 to 16 or so. These lower readings are more typical of poor metallic conductors such as nickel and lead. Now, it makes sense why using a lead target just might be closer to what the gold would indicate as.

This information helped clear up the confusion I had regarding the previously mentioned larger nuggets I have that read as low conductors.

Initially, I thought the reason these other nuggets generated a low conductive response because they were rough and coarse, but now, I suspect the reason to be because of their alloy content as much as the roughness.

What this information does for me is to warn me that gold can respond about any way possible. So, it really helps to know more about the gold being found in an area to get a better idea of what type of signal might be encountered, and even then, don't be alarmed if some specimen doesn't follow the norm.

In other words, using the single tone technique can have a very negative impact if the wrong assumptions are made. So, when in doubt, it is best to use the ALL mode.

On the other side of the coin, I have tested enough nuggets from certain areas around Rich Hill that I know many if not most nuggets greater than 1/4 oz or so, will create a high conductive response that I will use this mode in the real trashy areas. I also know I may miss some gold doing this.

Reg"


This all agrees with my observations. I think how a nugget will read is governed first by purity, as in percentage of gold to other alloyed metals. Second by the amount of included rock and how dispersed the gold is in the rock. A solid lump of high purity gold enclosed in rock will read different then the same amount of gold dispersed as stringers and smaller lumps in the rock. And then comes size.

Our gold at Moore Creek has quite a high range of fineness but averages around 850 fine (85% gold) the rest being mostly silver. It has lots of rock (which gets counted in the total weight of the specimen) and specimens that are half rock and half metal would not be unusual. The gold may be in a solid mass in the rock or dispersed in a moss-like structure throughout the rock.

So far all gold from Moore Creek including sapecimens of up to 3.5 ounces have read with a low conductive high tone.

I'm also convinced but have yet to prove that solid slugs of higher purity gold from other locations will go low tone at much lower weights. I will have access to a variety of gold from different locations to test soon and will report back.

This can be very helpful if a person can get a consistent tone of one type or the other at a specific location. I think high tone gold will be the norm, and at Moore Creek you can with 99% plus certainty ignore low tones as being hot rocks or large junk. At other locations a person might be able to target low tones as being larger high purity nuggets while ignoring the vast majority of small steel and iron trash but also while missing smaller gold.

Steve Herschbach