tridymiitillä

Tridymite is a high-temperature polymorph of silica (silicon dioxide, SiO2). It is one of the three common crystalline forms of silica, along with quartz and cristobalite. Tridymite is stable at temperatures between approximately 870 °C and 1470 °C at atmospheric pressure. Below 870 °C, it tends to transform into the more stable form, quartz, and above 1470 °C, it transforms into cristobalite.

Tridymite has a complex crystal structure that changes with temperature. It exists in several different forms, or modifications, depending on the temperature. These modifications are often designated by Greek letters, such as alpha-tridymite and beta-tridymite, reflecting structural changes upon cooling or heating.

It is found naturally in volcanic rocks, particularly those that have cooled slowly from silica-rich magmas. It can also occur in meteorites and in some industrial materials that have been subjected to high temperatures, such as refractory bricks. Tridymite is relatively rare compared to quartz and cristobalite.

Due to its high-temperature stability range, tridymite is significant in understanding geological processes involving magmatic and metamorphic rocks. Its presence can indicate specific thermal histories of rocks. While not as common as quartz, its identification is important for mineralogical and petrological studies.