Crystal (rock crystal) is a rare mineral, a type of gemstone, a quartz crystal, which belongs to the quartz group in mineralogy. Its main chemical component is silicon dioxide, with the chemical formula SiO2.When pure, it forms colorless and transparent crystals. It is pink, purple, yellow, teal, etc. when it contains trace elements such as Al and Fe. Irradiated trace elements form different types of color centers, producing different colors, such as purple, yellow, teal, pink, etc. Those containing associated inclusions are called inclusions crystals, such as hair crystal, green ghost, red...