Looks like maybe a mercury coating on some of those flakes?
I met some prospectors in their golden 80's years this summer that were learning how to prospect, and they sure didn't know what mercury coated gold was.
They had some silver colored flakes that were right heavy as they told me it always sat in the crease with the gold and the super heavies. They wanted me to look at some of that silvery stuff.
I ID'd it for them as gold for certain, and then I asked them what they'd done with the mercury coated gold over the two weeks they'd been high-banking. They'd thrown it out all over a steep hillside!
That's some crazy kind of catch and release gold story. They'd thrown away about a quarter of every clean-up until I told them what they were throwing away, and they were working some great dirt. They sure looked sick.
All the best,
Lanny