Minerals in Oceania?

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,...

No. Minerals may be changed by being melted and thus forming new different minerals upon freezing again. The new mineral will depend upon which other minerals were in the melt at the time. Further,...

The tourmaline group (cyclosilicates)

A harder mineral will scratch a softer one.

Chalk is a sedimentary rock composed of the skeletal remains of tiny marine organisms and is composed mainly of the mineral calcite. As such, chalk is not a mineral.