Silica (SiO2) is a very common mineral found in various forms, including:
* Quartz: One of the most common minerals on Earth.
* Cristobalite: A high-temperature form of silica.
* Tridymite: Another high-temperature form of silica.
* Opal: A hydrated form of silica.
These different forms of silica have different crystal structures, resulting in a wide range of properties and uses.
