Official websites use .gov
A .gov website belongs to an official government organization in the United States.
Secure .gov websites use HTTPS
A lock () or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.
Quartz is one of the most common minerals in the Earth's crust. It is made up of silicon dioxide (SiO 2 ), otherwise known as silica. This common, hard silicate mineral was used to make tools.
Public Domain.
