Marble is a metamorphic rock, formed naturally from limestone that is under great heat and pressure over a long period of time. It is often used as a building stone. Obsidian is ancient volcanic glass and was once widely used for arrowheads. This volcanic rock was called pumax by the Romans. Pumice is used for polishing hard things.
Nobody seems to know where the German word came from.
Quartz is an abundant mineral. Most sand is made up of small pieces of quartz. Quartz is important in glass making and in electronics. It is also used for sanding hard surfaces. It is used as a building stone.