Detecting in Gold Mines
A couple of weeks back I was invited to inspect two gold mines that happen to be the closest mines located to Melbourne Vic. These mines were very rich and were mined up until 1905. These mines are currently under mining lease and should not be entered unless permission is given. One mine is a straight cut into the side of a hill and perfectly safe to walk in up to the 100 meter marker on the wall, after the marker there is an area that was stoped out and currently it is unstable, pity we could not access this area as there has been some beautiful specimens found in this stoped area.
The other mine on the lease is multi level and goes down 400ft and there is no way in hell that I would venture down this mine without all safety gear, but on a different note there is a suspected untouched reef between the two existing mines. There is a river or creek at the edge of the lease that has plenty of nice pickers when it has been panned by the current owners. The reason for going to the mines was to test some very sensitive modifications to pulse induction (p.i) metal detectors, in this case I installed some new low noise circuitry into the detector and modified various parts of the circuit to run faster pulses that greatly improved the detection of small specimen gold.
Being underground there is next to zero electrical interference and thus a lot more input gain can be used to give some exceptional depth on specimen type gold but we also found it was extremely good on small nuggets as we found testing with a 10’ X 15’ coil. We found a near 2 gram nugget in an area of a small quartz leader. After chipping out the quartz we found the target well over 12 inches into the wall. There seems to be a lot of iron junk on the floor of all these old mines and having the old metal rails for the ore carts make it impossible to detect the bottom.
Many years ago I was detecting the inside of a mine at Yandoit in Victoria and was using a discriminating vlf detector that happened to be an old first edition whites gold master.
I dropped the detector when a couple of bats went past my head and on picking the detector up it was giving a loud signal, after a minute scratching around in the dusty mine I found a near mint condition half sovereign. No more treasure was found in that mine as you may of guessed that I worked it over very carefully.
Using a p.i type detector will give a depth advantage on larger gold in these mines but most of the gold is small and thus the modifications were carried out to get good depth penetration on small gold in a low noise environment. The mining lease that includes these two mines is on currently on the market, My thinking is that the straight cut and stoped workings would be fairly easy to bring back online but the big deep one would need a lot of money spent to bring it up to an acceptable standard, I was thinking of buying into this mine as historical records show that many thousands of ounces were recovered from the deep mine and I have detected gold in the side walls of the smaller mine. It just gets me pondering what lies beyond and around the stoped out part that yielded the larger nuggets of gold.
Too much dreaming here as my work load does not allow me to go and work a gold mine, but if any person is interested I can can put you in contact with the the people in charge. All these mines need work carried out to make them safe, and I would strongly advise not to go down old mines as some have false bottoms that go straight down into the abyss, some have stale air and others are just unstable. There is another interesting mine that I accidentally discovered a few years back when I jumped into an old miners hole at Creswick in Victoria and had my leg go through the ground into a cavity.
I was curious to see where it went and the small hole opened out into a mine that had been dug under an old river bed, the old timers had removed the silty bottom and left a fantastic looking natural ceiling made from quartz rocks and conglomerates. After a few days I went back to the old workings with a friend and we wiggled our way in.
I was detecting the rock ceiling while he was behind be with a small pick and bucket.
Roughly 20 meters along we came to a big widened out area that had a middle piece of river bottom left as the centre support, I said to my friend to take note of the wash layers and I pointed out where the gold would of been, I was on my back with only four or five inches to the ceiling and I was squirming along and detecting the quartz ceiling when I could hear the sound of tap tap tap and thought to myself that my friend was gathering some rocks or something but after a while I thought to myself I better wiggle back and see what he was chipping at.
I nearly had a fit as when I got back to the widened out part he was busy as a beaver removing the bottom of the central support. There was a lot of some very choice words coming out of my mouth and boy did I get out of there fast. To make matters worse I jumped in and out of the old miners holes in a direction to get back to the car to have a drink when just as I was about to jump I hesitated as I could see something in the hole, there were two tiger snakes coiled around each other. I nearly jumped right on top of them and spoiled their fun and they would of surely retaliated.
Then I was starting to think that those snakes were not very far from where I went underground, imagine wiggling into the darkness in limited clearance 20 meters or so along when you hear something hissing near the back of your head. Since that time I have avoided getting into mines that I cannot freely walk into. Over the years I have detected a large number of mines and at least 80% give you nothing but some do have break away quartz runs that look very thin on the wall but can grow in thickness and this is where I find the nuggety gold in most cases. I would 100% avoid chipping into a mine wall if the ceiling is not 100% intact and in all seriousness it is much better swinging the coil out in the sun and fresh air, disturbing old mines can be a risky business.