Kyanite is a common metamorphic silicate mineral, usually bluish in color, though it can appear in shades of grey, black, blue, pink, white and yellow. It is usually found as bladed crystals, though radiating masses of crystals have been known to occur. Kyanite can expand up to twice its original volume when heated.
Chemical composition: Al2(SiO4)O; Hardness: 5.5-7
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