Is there anything inside this rock?

Hi all, About 18 months ago I was in Collinsville, ( it's a coal mining town) 85 ks inland from Bowen. I have an investment property. When I was there last I decided to take my detector with me & give the surrounding nearby area a bit of a go. There are heaps of hills with a ridge of rocky granite & basalts stretching probably 15-20ks. I know from what I've researched that gold mining was quite polific around the early 1900's. There'd be at least 20 mines stretched out from north of Mackay ( inland ) all the way up to Proserpine ( inland). What Iv'e read it was mainly reef gold, no mention of any nuggets or alluvial gold. The area looks so promising I just had to have a try. To keep this thread as brief as possible, I was detecting in a dry creek half an hour out of town, when I got a positive signal coming from this lump of rock! I was using the 11'DD original minelab coil on my GP3500. If I knew how to download photos I would cetainly done so, but I will describe it the best I can. The first thing I noticed was that it was very heavy for its size: around 15cm long,5cm thick at one end, 10cm thick at the other, and 9cm wide. It weighs just over 3 kilos. It is smooth on top, maroon reddy colour with a bit of grey, there is a fine seam of quartz ( 1mm ) going completly along & around it. Underneath is rougher,dark brown to light brown. There seems like a bit of other minerals are showing, some black specks ( maybe mica) & a little bit of black & white granite. Interstingly I can scratch the most of the surface with my thumb nail, even though it seems hard. It's been lying at the side of my garage till now, as I am not sure what to do with it. I've heard of hydrochloric acid, but haven't used it as it's s'pose to be a dangerous acid. Cutting the rock in half with my tile saw also came up, but I could devalue it, if it does contain what we are all after. I'm sure other people have faced the same situation, so I'm asking the experienced fossickers out there what should I possibly do? Any useful advice will be muchly appreciated, cheers Davo

I'm afraid curiosity would have got the better of me by now and I would have smashed it the day I brought it home.

just a thought, if you can find a rock of similar size and dimentions, weigh it

G'day - run a gpx4500 over it in Enhance... chances are the signal will be gone, but if it responds, as tuna says above, smash it up!

cheers - trashdigger

Hi Davo,

During the last PMAV meeting a guy showed us a rock (it was called conglomerate if I remember right) he found in a sort of similar situation. When he run over it with the detector it gave positive signal. He took it home and cracked it open with a hammer and chisel. Just where it cracked, on one side was a little - approx. 1g - nugget.

Cheers
Ralph

I test these targets by rotating them while swinging them over the coil, adjusting the distance away from the coil. Then pick the strongest area that the signal is coming from. If the signal is coming from a sharp corner than its usually not gold. If you have the machine in tracking then you will most likely hear the signal getting weaker as the machine tries to tune it out, if its not gold.
If the signal has you still wondering (they all should) then place the target on a hard rock and use your pick by holding the handle and crushing with a vertical drop on top of the target. If your lucky you will have an even stronger signal from one small fragment or worse, you will have lots of little signals from many pieces or no signal at all. There is lots of types of rock that can give a false signal. Conglomerate on the other hand is one of the most exiting types of rock to get a signal from as it is all types of rock and minerals that were once separate that have now, due to the wonders of nature been forced back together as one lump. Gold could easily get caught up in the mix.
Brett.
PS. break it open is my thought.

I would run a strong magnet over it to start with - it's amazing how sometimes you forget to eliminate the obvious. If it still shows up as a non ferrous mineral, I would be putting it under the hammer to satisfy my curiosity. If it does contain gold, it will be worth more as a specimen with the gold exposed.

caveman

I forgot to mention that I would not try cutting it with a tile saw simply because if there is a lump of the yellow stuff inside it, you definitely run the risk of damaging it. Smack it with a lump hammer would be the best option and it should split along cleavage lines - if you still cannot find gold, then dolly it and put it through a pan.

caveman

Thanks to all for your tips, I don't have a GPX4500, but I will do all the other suggested tests, will get back to you soon, cheers Dave

Before smashing anything, consider doing what Archimedes did, 2000 years ago.
Find out the specific gravity of your rock and compare it to the specific gravity of known rocks.
http://www.edumine.com/xtoolkit/tables/sgtables.htm

From there, you can draw your own conclusions.

See you up them thar hills,
Frank

Hi Gang, Managed to split my rock into 8 pieces, unfortunately no sign of that" golden" stuff. Caveman was on the ball, used the magnet & 3 pieces were strongly attracted to it. So looks like "Mr Ironstone" gave me the false signal. I'm still keeping the pieces, who knows when I get myself a dolly pot & pan it all, what I may find, - ah well back to reality, thanks again to all for there good suggestions, & may you strike it rich! Dave

That's the first brave step, done.
Its hard to make the decision to break open a target rock, for fear of doing it wrong.
I take those types of targets back to the mates. We are like kids listening to the signal and guessing what it may be or how big it might be.

And they say: Santa doesn't visit us adults? I love unwrapping those little presents. Even if the result is an empty present.
Brett.

hi
quite a few times i have detected rocks that gave off a terrific signal and have been totaly convinced there was a piece of gold in them.most of the time i have smashed them open there has been nothing there.
   i now realise what causes this. whether you are using the latest & greatest minelab or an old garret A2B,for your machine to work properly it has to tune out the minerlisation of the ground you are detecting on,these super hot rocks that give off the fantistic signals have massively different minerasilation than the sourounding ground that they are laying on.
many years ago i found a black rock about the size of a golf ball that gives off a signal as big as a bucket.i took this rock away detecting a few times and what ever ground i dropped it on it gave a terrific signal.  BUT
 when ever i did an air test on this rock it gave off no signal at all.
if you do find a rock that you really like the sound of,do an air test on it. get it up high on a tree stump or anything to get it away from the mineralisation of the ground it was sitting on.if you can then tune the rock out to the point where you cant hear it,it probably does not have gold in it.

be carefull of the magnet test also, i have seen nuggets with a good coat of ironstone
that can be picked up with a magnet.
cheers fencejumper

Just for a bit of fun but true, The mate put his coil over a large quartz boulder, bloody machine screamed . Had to be gold and lots of it we thought,smashed the rock to bits and pin pointed the source, turned out to be a bullet lodged in a crack in the quartz.