Final answer:
Quartz is the most common type of crystalline silica, used in a variety of applications from jewelry to frequency control in electronics, and also in the production of amorphous silica products.
Step-by-step explanation:
The most common type of crystalline silica is quartz. Quartz is a hard, brittle, clear, and colorless solid that is widely used in various applications due to its physical properties. It is found in abundance in the Earth's crust and can be fashioned into semiprecious jewels and used for architectural decorations. It has significance in the electronics industry as well, especially in frequency control for radio transmitters. Despite the existence of other forms of crystalline silica, such as cristobalite and tridymite, quartz remains the predominant form. Additionally, the term quartz is applied to certain manufactured products made from amorphous silica, like tubing and lenses. At high temperatures, quartz melts and can be cooled to form fused silica, an amorphous solid with properties useful in UV-light-emitting lamps and optical instruments, as well as in household items like ceramic cookware which contains amorphous silica.