I don't think so. I think it's made of minerals, but not actually one.
Sand and gravel are rock particles that are made of various minerals.
placer deposits
Generally clays. Perhaps you've seen some makeup bottles labeled with something like "kaolin". "kaolin" is referring to kaolinite clay. I've also heard of montmorrilonite clays being used in makeup,...
A harder mineral will scratch a softer one.
yes yes it can