Quartz from Brazil (No.17)

Quartz is the second most abundant mineral in the Earth’s continental crust, after feldspar.

It's made up of a continuous framework of silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2

Quartz crystals are said to amplify both body energy and thoughts and may provide for clarity in thinking to enable thoughts to more effectively influence matter.