Final answer:
The mineral composed of pure silicon dioxide (SiO2) is quartz, which is a common, diverse mineral used in various applications, from jewelry to technological devices. It is the most prevalent crystalline form of silica and constitutes a significant portion of the Earth's crust.
Step-by-step explanation:
The mineral composed of pure silicon dioxide (SiO2) is quartz. Silicon dioxide, also known as silica, appears in nature in both crystalline and amorphous forms. The most common crystalline form of silicon dioxide is quartz, which is found in all rock types and is the stable polymorph at the Earth's surface.
Quartz is a hard, brittle, clear, colorless solid that is used for a variety of purposes, such as architectural decorations and semiprecious jewels. Additionally, it plays a role in technology, for example in frequency control in radio transmitters. Some quartz varieties may have different colors due to trace amounts of impurities, like Fe3+ giving amethyst its purple color. Articles such as tubing and lenses manufactured from amorphous silica are also often referred to as quartz. However, other substances like asbestos, calcite, and zircon have different chemical compositions and are not made of pure SiO2.
The silicates, which include silicon dioxide, are a large and complex class of minerals, making up about 90% of the Earth's crust. The basic building block of these minerals is the silica tetrahedron, which represents a structural combination of four oxygen atoms and one silicon atom.