Hello, I was tramping around some old mines in the Coromandel and found what I think is Quartz on iron ore (dark shiny black with bleeds of red) - theres lots of sparkly little crystals on it which is what caught my eye (sadly no sign of gold) - can anyone please confirm?
Grey could be a sign of silver. Is the rock heavier than normal?
Best to crush it and smelt it.
You can easily smelt with a fire buried in the ground.
If it is heavy with shiny black areas which appear semi crystaline in form and shiny then likely galena which is an ore of silver
My thought is that it could be sphalerite.
Galena is in the same volcanic-hydrothermal (epithermal) association. However Galena has a greasy appearance, and tends to massive rather than quartz like.
The black may also indicate sulphides.
So in that ‘gold mine’ grouping that extends down the east side of the Coromandel, Waihi and Te Aroha includes:
gold-related:
pyrite, FeS2
sphalerite, ZnS
galena, PbS
arsenopyrite, FeAsS
chalcopyrite, CuFeS
Still a great mineral specimen.
K8
When I get back from Dunedin I will try to photograph a 25kg block of galena from the Tui mine - it is not greasy but as I described above however the rock could have any of the above you list in it.
thanks for the suggestions guys, I looked around at various pictures and sphalerite looked most similar, i smashed the rock open with hammer (harder than I thought) & lots & lots of little spiking crystals everywhere inside, I crushed majority of the thing into powder minus some hard bits that just wouldn’t smash - sadly no gold 
The gold may not be visible, you need to smelt it.