well no.4 has fools gold I think...so its a no lol and number 19 is granite I'm pretty sure, and the ridges are hard just like the rest of the rock...but on the underside theres this very red colour...i can take a pic if needed?
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?
1 ) you are correct the red is from ferric oxide. in a heavily planted tank the plants should use up the Fe before it has a detrimental effect on the fish.
2 ) do you mean Labradorite? if so it is a plagioclase feldspar and is therfor unsuitable for long term aquatic use.
3 ) micas are complex hydrous potassium-aluminium silicate minerals. There are more than 20 chemically distinct mica types with considerable variance in geologic occurance, but all have essentially the same crystal structure. none of them are suitable for use in aquariums
that really depends on the kind of shale
obviously Bituminous shale and Oil shale are not going to be good
whereas generally speaking Slate, Siltstone and Mudstone are ok, dependant on the other impurities in it.