I think this is cinnabar.
The shiny metalic purple area rubs off easily onto fingers (yes I quickly wash off), the rock is damp from river. What you see is inside of a fresh broken piece.
Can anyone who’s more familiar with it confim my guess?
Top view:
I thought cinna bar was a hot chick that was called cinna and worked behind the bar. don’t tell my wife that I’m chasing cinnabar
Becareful, both can be dangrous. 
Ngawha was mined for cinnabar
Couldn’t find any pictures of Ngawha cinnabar.
Did find some pictures of Puhipuhi cinnabar:
Mine does have some yellow in the back (sulphides)
Perhaps I only have some Ferrous rock 
It only appears to have minute quartz.
I’ll do some chemistry on a small bit and put it under a microscope - see if I can find the gold 
And there I was having flashbacks to the Whittakers Cinnamon Chocolate coated toffee bars 5c each from the corner dairy
It does look a little like Waitahuna cinnabar so one never knows but there will be tests that you can do. If it is then it’s a nice specimen and I would be almost prepared to bet that it is richer than the Puhipuhi samples which are nice looking but not near as rich as the Waitahuna Heights samples.
That chunk was about the size of my fist. I broke it off a much larger piece.
Found another large piece too, not quite as good looking.
Aw if it’s cinnabar then me is jellyarse. Is it quite heavy for it’s size. If so then that might increase the possibility as the only larger size piece I saw from the Waitahuna Heights mine at Waipori was heavy for it’s size.
Nah, it’s light. I reckon I’ve got some pretty ferrous rock 
Oh well ferrous with a possibility of sulphides is still a good rock.
I saw some Coromandel rocks the other day that soemone had and I for one would go gaa gaa if I found them - truly amazing specimens.
