Quartz is a crystalline form of silica. The greatest concentrations of quartz are found in silica-rich igneous and metamorphic rocks. Often transparent, Quartz can be found in almost any color. Quartz has piezoelectric properties, meaning it generates an electric charge in response to pressure.
Chemical composition: SiO2; Hardness: 7
Inclusions happen when foreign matter is captured within another mineral during its formation. Such inclusions can verify a specimens’ authenticity and give clues to its origin.