FMF - Friends of Minerals Forum, discussion and message board

[auProspector]

Hi again!

I'm a prospector for gold in FNQ Australia. While metal detecting up a random gulley (using a high-end pulse induction detector with a small mono coil), I found a few of these little targets, all separated in different areas of the gulley by at least 50-200 meters. They sounded highly conductive (even with pin pointer), and like gold all buried at least a few inches down, and are relatively small -- not at all like the typical "hot rocks" I come across.

To the naked eye they just looked like random little rocks, no signs of any metallic surface/luster. The patches of white you see appears to be oxidation

They're quite light in weight. Certainly not encrusted lead or any of the heavy/dense minerals.

They're not at all magnetic.

I checked each with a multimeter to see if any continuity when putting the probes at any points on the surfaces... nothing.

I tried lightly hammering one of the pieces and while some tiny fragments came off, it for the most part just flattened out a little... so does appear malleable. After hammering it which removed some of the outer crust (though still couldn't really see any metallic surface at least to naked eye), I tried the continuity test again with the multimeter and this time was able to get continuity in a few points all over.

I then decided to drop it in a dilution of sulfuric acid, seemed quite reactive, left it for about 10 minutes. Pulled out/rinsed, and it seemed much darker. Now it has continuity no matter where I touch it with multimeter probes. Still not magnetic in the slightest. Doesn't leave much of a streak on white paper (unlikely to be graphite).

One in the middle is the one I was testing on. The other 2 are as I found them.
I can try get some better close-up pictures when I get ahold of a better quality camera.

Any clues?!

[James Catmur]

Take photos of them on plain white paper, that way the camera focuses on the specimen and not the background/your finger.

To test the streak, use the back of a white unglazed ceramic (i.e. floor tile).

Test the hardness too