Calcite is naturally colorless or white with a vitreous luster, though the introduction of other compounds during formation can result in a variety of colors. It is best known for its characteristic rhombohedron crystallization though it can be found in various forms.
Chemical composition: Ca[CO3]; Hardness: 3
Hematite is a common iron oxide that is sometimes magnetic. It is iron, grey in color and is found throughout the world near the earth’s surface.
Chemical composition: Fe2O3; Hardness: 5-6
Quartz is a crystalline form of silica. The greatest concentrations of quartz are found in silica-rich igneous and metamorphic rocks. Quartz is one of Earth’s most abundant minerals and is an essential component of granite and many other rocks. Often transparent, Quartz can be found in almost any color. Macrocrystalline Quartz is composed of visible crystals, microcrystalline Quartz is densely compacted microscopic quartz crystals. Quartz has piezoelectric properties, meaning it generates an electric charge in response to pressure.
Chemical composition: SiO2; Hardness: 7