Quartz is a crystalline mineral composed of silicon and oxygen atoms, with the chemical formula SiO2. At room temperature, quartz is a solid. It is the second most abundant mineral in Earth's continental crust, after feldspar. Quartz has a high melting point of 1713 degrees Celsius (3115 degrees Fahrenheit) and a high specific gravity of 2.65. It is a very hard mineral, with a Mohs hardness of 7, which makes it resistant to scratching and abrasion. Quartz is a common component of granite, sandstone, and other igneous and sedimentary rocks. It is also found in veins and as individual crystals. Quartz has a wide variety of uses, including in jewelry, countertops, and as an abrasive.