Quartz is our most common mineral. Quartz is made of the two most abundant chemical elements on Earth: oxygen and silicon. Atoms of oxygen and silicon join together as tetrahedrons (three sided pyramids). These stack together to build crystals. Billions of tetrahedrons are needed to build even a small crystal. Quartz is an almost pure chemical compound with constant physical properties. Quartz makes up about 12 percent of the land surface and about 20 percent of the Earth's crust. Most of the remaining crustal rocks are rich in silicate minerals which include silicon and oxygen together with other elements. Quartz is divided into two groups; crystalline or visible crystals and cryptocrystalline or hidden crystals which, require a microscope. The size is 4.9 x 1.9 x 1.3 CM