Couple rocks I'm curious about:
1) Red Shale - Now I know this is just red clay that's been pressed to a sedimetary rock, but red tends to equal oxides of iron. I've been using this in several planted tanks. Figure I ought to be worried? Plants seem to be doing fine. Mostly I ask because this is the single most common rock there is where I am. Any construction site has to dispose of tons of it.
2) Lapiderite - Beautiful rock - White/grey matrix with hordes of tiny silvery purple microcystals all over it. Unfortunately, at a guess I would say it was a calcium based rock with mica and amethyst inclusions, but I have not been able to find it on the wb and I haven't managed to unearth my minerals book lately.
3) Mica - Just thin sheets of silicon oxides, nu? Should be ok?