By BT (GMT Goldmaster - discontinued)
I have always had a soft spot for the GMT Goldmaster’s, especially their amazing sensitivity on small gold nuggets and specimens. But the use of them in the past was limited due to the fact that they were hard to keep under control in the heavy iron-stone-laden fields of Victoria’s golden triangle, not impossible I might add but hard.
But I must balance this by saying that I do know a few people who use them in these fields and have enjoyed quite a degree of success. For me though, the constant ground balancing would sometimes beat me but maybe I’m just lazy. Anyways when I heard that White’s were releasing an all-new Goldmaster with auto tracking and heavy ironstone workability, I was eager to check one out.
When the chance came I decided to try it out on some flogged digging west of Dunolly, Victoria. Having used Goldmaster's in the past I knew that the pre-set marks of 7 to 8 for the gain and 3 to 4 for the V-sat control would probably be a little high for Aussie conditions. I tried them anyway but guessed right judging by the ground noises being made as I swept the coil after balancing. I must admit that when they say it has fast auto track they aren’t kidding as it balanced within two pumps of the coil. I lowered the gain by one mark and raised the V-sat by one and so on until the detector was purring away contentedly as I swept the coil back and forth.
Above: The number in the upper left of the screen show the type of ground or ‘mineralistation’. Higher numbers for negative-type ground and low numbers for positive-type ground mineralisation, the numbers in the upper right of the screen show the amount of mineralisation. This is the part of the meter that is used to locate concentrations of “black sand” in creek beds and so on.
Before starting to detect I placed a small test nugget of about a gram a few inches under the ground to see if my settings were right. As I swept the coil back and forth I played with the gain and V-sat to try and get the best response. I learned this trick from a book called Zip-Zip written by Larry Salle from the United States.
Happy I was tuned in properly, I began to detect. The auto tracking was great, enabling the machine to keep up an even threshold in the hot ground I was working. If for any reason I had to remind it to, which was not often, all it took was to hold the “grab” pad down and give it one pump. Nice to see a machine do as it’s told for once. I have used auto trackers here before and though successful they were unruly at times.
It wasn’t long before I was digging up shotgun pellets and the odd .22 bullets. After about 20 into it one signal was finally the right colour. Not big but right colour nonetheless, about third of a gram I guessed, at about an inch deep and a good clear signal. I detected a heap more pellets and bullets and an old nail to go with them.
The nail discriminated but I checked it anyway as I wasn’t overly familiar with the new system the GMT Goldmaster uses. It has three types of discrimination – constant probability bar graph: no depth loss; and trigger forward adding audio “grunt” or trigger held towards you for digital analyser. From what I had seen, it was a good system.
A week later I brought one of these machines and was standing at one of my favourite spots ready to go. I knew the ground conditions here were milder that at Dunolly so started out with the gain set two points higher. My former settings had been at 4 but here I was able to increase it to 6 with the V-sat also on 6. The V-sat in Dunolly was set on 8. These settings gave me the best target response on my tester. There are a few areas here with a fair amount of iron junk which would also give me a chance to get used to the new ID system on the GMT Goldmaster, as well as hopefully finding some gold.
I soon had a heap of pellets and bullets to show for about half an hour’s detecting as well as some discriminated bits of iron that I was still checking until I gained more confidence in the “grunt”. The next target sounded different from the rest, a lot like my tester, and after digging about three to four inches down I unearthed a nice little specimen with roughly half a gram of crystalline gold stuck to it. This made me pretty happy as this particular bit of ground had been rather annoying on past visits because of all the iron fragments littered throughout the dirt and quartz debris. The new ID system was winning me.
Above: Specimens pieces found on “thrashed” ground by the author during the first couple of outings, as well as a couple found on the day the photograph was taken.
A couple of trash targets later saw two more small bits of gold surface, about a third to half a gram in each, but again the right colour.
Approximately thirty minutes later and a few more targets later, another good sound that turned out to be another specimen containing about one gram of nice sparkling gold. I was really enjoying being able to wade successfully through junk with little effort. By this point I was sold on the reliability of the ID, especially the “Trigger-towards-you” analyser. It was proving itself spot on for iron trash.
In my past expeditions here I had used a big quartz boulder to smash up large specimens that were too big to take home and that had too little gold in them to make it worthwhile keeping them intact. I thought it would be worth a look around for any small bits I might have lost while on my smashing spree as there must have been plenty of them.
This turned out to be right because within five minutes I’d recovered three such pieces in the rubble. They only contained bits of gold around one-tenth of a gram but my previous detectors had been unable to locate them.
Just away from the boulder I got a really good sound and started to dig it out, hoping to pull up a nice nugget or specimen. At about a foot deep out came a piece of melted lead that would have weight about half an ounce. I was unhappy about the fact the target was lead but very happy with the depth at which I’d detected it. When you’re getting targets a few inches deep you start to wonder whether or not you’re getting depth. When you do get a deep target, regardless of value, it’s a reassurance worth having.
The clay had drawn on and before leaving I wanted to check out the new mineral reading meters that White’s have incorporated in the GMT Goldmaster. One gives mineral type readings – high numbers for negative ground like ironstone and lower numbers for positive (alkali) type ground. They read from 0 to 99. The other meter lets you know how much mineral is present. The latter is called a “black sand” meter which I imagine would be perfect for people who like sluicing or panning.
It apparently is being used by prospectors in the United States to locate gold-bearing black sand deposits in creek beds and other such places. These two meters are all new to detecting and I predict they will prove to be a winner here as well.
This place was perfect to test them out because several years earlier an old prospector had located a small leader next to the reef and it had netted him more than seven ounces of crystalline gold worth small fortune to collectors. The vein was about 20 feet long and only an inch or two wide. I followed the instructions and pumped the coil up and down as I followed the small leader.
The readings were low, around 60, as the machine displayed the values but as I neared the spot where the old guy had found the gold, the reading jumped to more than 90. Away from it and the readings were back in the 60’s. I was convinced that the type of pocket of gold won by the lucky old fella could also be easily located by the GMT mineral meters.
Even if there was no signal and the gold was fine, who wouldn’t check out such a reading jump when following a quartz vein? It got me thinking, I can tell you.
Another thing the GMT has going for it is that you can also run it in manual mode and do the ground balancing yourself. Some people like to run their machine on the positive side which can bring up the response to small, deep targets – something not possible with auto tracking.
The “grab pad mentioned earlier works in manual as well. As well as that, there is an inbuilt boost switch that does away with the need for amplifiers. This certainly is a well-thought-out unit.
To sum up, the White’s GMT is fun to use and light to carry and opens up some very interesting detecting possibilities using the meters. It doesn’t take long to get use too and the new ID system can take you where others have given up. It is not always the deepest searcher that gets the gold.
A machine that is easy to carry and learn and has a healthy balance to intelligence and controllability goes a long way.