Warm vent rock

[salvageon]

My friend has some warm vents on his property that melt the snow in the winter and we built some road through the slide and found this. It's a very thin vein and almost oily feel. Do you have any idea what it is? I told my friend that if we kept digging we'd uncover a volcano and he'd be in trouble with the neighbors.

 

[Eu_citzen]

Can you scratch it with a knife? Magnetic? What colour do you get if rubbed against an unglazed piece of porcelain?

 

[salvageon]

I tried scratching it with a knife but it wouldn't. Also it's non magnetic and I will have to try to find some porcelain. Thanks