Quartz
Quartz is a mineral with the chemical formula SiO2 (silicon dioxide).
Physical Properties:
Color: Quartz is usually clear or milky white, but can also be colored by impurities to form various shades of yellow, pink, purple, and green.
Luster: Quartz has a glassy luster.
Transparency: Quartz is transparent to translucent.
Crystal habit: Quartz forms as hexagonal prismatic crystals or as massive aggregates.
Hardness: Quartz has a Mohs hardness of 7.
Specific gravity: Quartz has a specific gravity of 2.65.
Cleavage: Quartz does not exhibit cleavage.
Fracture: Quartz has a conchoidal fracture.
Magnetic properties: Quartz is not magnetic.
Optical Properties:
Refractive index: Quartz has a refractive index of about 1.544 to 1.553.
Optic sign: Quartz is isotropic.
Dispersion: Quartz has a low dispersion.
Pleochroism: Quartz does not exhibit pleochroism.
Birefringence: Quartz does not exhibit birefringence.
Extinction: Quartz has a low extinction angle.
Interference colors: Quartz does not exhibit interference colors.
Relief: Quartz has a low relief.
Uses:
Quartz is an important industrial mineral, used for its high silica content and its mechanical, thermal, and electrical properties.
Quartz is also used as a gemstone, decorative mineral specimen, and for religious purposes.
Please note that these properties can vary depending on the exact composition and impurities present in the mineral specimen.
Source - INTERNET