Can anyone tell me what this is please

Hi guys just wondering if anyone can explain what this is for me. I have been finding bits of this around old diggings and was wondering what it was. Some pieces of gold I have found have been covered in the black as well so I am trying to work out the story behind it all. Excuse my lack of knowledge I am just trying to work out what the old timers were searching for in this area.
Any help greatly appreciated.

There are some geo's on this forum so they will know for sure??
To me it just looks like conglomerate rock eh?

Was there an old smelter in the vicinity?
Mackka

Not that I know very much, but could it be a conglomeration of some sort.

I should have added its in the Ararat area. I will try and post some more photos of it around the diggings when i can

Definitely cemented gravels/conglomerate IMO.
The Hard Hills area north of Ararat is known for these.
"Hard Hill contained a lead of Tertiary or older high level gravels which were cemented together into a hard conglomerate."
I would be looking for evidence of eroded areas containing these cemented gravels/conglomerates. I think the old timers may have removed most of it from the diggings to be crushed/sluiced to get the gold. Certainly worth running your detector over any lumps of it you see.
To me it looks like quartz & a mixture of other old river gravels. Again IMO the black colour would be an oxide crust from the degradation of iron rich rock in the area I.e. basalt not so much the colour/type of rock you need to look for but a good indicator if your finding gold where the oxide is present.
Hopefully one of the Geo's can confirm or debunk my theory.