I've been trying to polish a rock my brother found on the beach a year ago which he picked up and put in the garden because it looked shiny.
It seems to look dull when it is in water but then crystallizes as it dries out. Also there seems to be a white powder/crystal in the cracks and a pink and yellow colour in the veins. It also seems to absorb water and does look and feel slightly fibrous.
I'm now a bit worried that if it is serpentine it contains asbestos. I used the dremel on it whilst sitting in the conservatory and although I did put a scarf over my face and was careful not to breathe in any of the dust, I wasn't too worried about it until now. I have since hoovered and wiped everything in the area I was in.
Difficult to say without a thin section to look at under the microscope.
But I could quite believe it is a piece of serpentinized dolerite. How much serpentine it contains, again I can't say from looking at the 'outside'. But if you're seeing fibrous areas, that's probably a good indication. Bear in mind that serpentine may also be present in the rock in a non-fibrous form.
From a human safety/health viewpoint, bear in mind:
- serpentine is a group of minerals
- only some forms of serpentine are used as asbestos (primarily chrysotile)