Black stuff on Quartz??

Hi guys, I came across some nice looking quartz while out detecting the other weekend and some of it has a black bitumen looking substance on it, was found near and old mine in the middle of the scrub and wondering if it's what they refer to a black leather or is it decomposed slates?





I also found some other interesting looking rock that I'm yet to crush.

oxidized ironstone mate the black is the greenish would be shale or sandstone that's attached to it

There is an area not far from Dunolly that produced a fair bit of what we called 'black gold', and was
encased in oxidised ironstone.
I wonder how many blokes threw them away thinking they were hot rocks?

Thanks HYT, had me puzzled why they'd have bitumen in the middle of the bush, I need to study geology more I think :/

To me the black / orange / brown thin coating is oxidised iron and the thick black heavy mass between rock is manganese dioxide used for dry cell batteries.

If its not, you may have a indicator line that the old timers would follow. get out a scope and look for pyrite cubes in the think black. Most likely not an indicator as I cant see lamination or a slate with it

High AtomRat, yes it's the thick black tar like mass that I was asking about, probably not the best pics but it looks like the stuff they fill road cracks with and was on a fair bit of the quartz around the old mine. It's in the Talbot area if that's any help but I was just curious as to if it was natural or placed over the rock in processing for any reason.
I'd not seen it before and learning a bit at at time, leather jacket was the term I was looking for in the OP not back leather.

Very nice looking rock I would crush it up and have a look what's inside. Good luck

Definitely manganese oxide ...im more interested in the small cubic void in the top pic...ex sulphides are a good indication of a mineralised vein...the surface stuff is all secondary weathering

When I picked up one piece of rock a small pyrite fell out but it was too hard to find in the leaf litter at the location, these rocks were from 2 different locations that I've marked on my maps for next time I'm out there and will spend a lot more time at each one.