Quiet gold

First topic message reminder :

G'day, had an unusual occurrence yesterday whilst out detecting and wondering if anyone else has had the same thing happen to em.
Found an area where there's a bit of small shallow gold about and a few sunbakers sitting on a ironstone/laterite flat. Some of the bits I've been getting are down to 0.1 of a gram.
Using a 17 elliptical n/f coupled to a 5000 yesterday I specked a nugget on the deck and then put coil over it, obvious screaming signal followed.
After walking a further 10 metres I specked another nugget sunbaking and put coil over it but no signal!
Picked nugget up, rubbed it on coil, still no signal!
Took it to a mate detecting nearby, he has a 5k also but using an 18 elliptical n/t coil. Dropped nugget onto his coil and still no noise.
The two sunbakers I got are almost identical in size but one has more mass so is a little heavier (.90 grams)
The other nugget is porous, same size as first sunbaker but weighs .30 grams. Yet can't produce a signal.
Tried using a 14 by 9 coil on the quiet nugget and it finally produced a signal. But only just.
I've never had or seen this before.
Settings I used with the 5k were fine gold, 18 gain, 12 stab , audio type normal, search mode general.
I tried using sharp as a soil timing to get a signal but still nothing.
Took some video footage which I'll try to upload over the weekend but will get a pic up for now of the two pieces of gold.

the plot thickens, this is a very interesting bit of gold. bring on a ATX,

I don't know about others, but I've used mercury to amalgamate fine gold, and even though it is thumb nail size, the detector doesn't give a signal, because it porous too, once melted down it is solid and there is no problems, the signals are not sent back to the coil from the porous gold, and the faint signal that you heard would have been from a small piece that was in there, just enough to send the signal back to the coil, I know we were also surprised that the detector wouldn't sound off on something that size, but there you have it, it must be a solid piece to get the signal

You are right about porous not giving a signal,but that is where it stops.
Eric Foster,who made P.I in the early days,was at the Archaeological Research Laboratory,he did some test on P.I machines,with a set of gold standards,same sizes and thickness,at 100% gold detection height was 7.5 inches,then add 10% silver,or copper to the sample and the range dropped to 3 inches,then to 80/20 and the range dropped to 2.25 inches,this stayed much the same until 20% gold and 80 silver or copper was in the sample,as the gold ratio dropped the range rose again,to the 7.5 inches when pure silver or copper.
The conclusion it is different metals in the target that effect the detection range.

The Digger