Quartz, with a chemical composition of silicon dioxide, is one of the most widely distributed minerals in the earth's crust. It's form is hexagonal, prismatic and crystalline, and it has a hardness of 7. Quartz comes in a variety of colors and forms including amethyst, citrine, ametrine, and rose quartz. It is a gemstone often taken for granted because of its affordability. Smoky quartz has brown tones which are also transparent due to a chemical variance at the time of composition.