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Related to Tridymite: cristobalite


SiO2 A white or colorless crystal occurring in minute, thin, tabular crystals or scales; a high-temperature polymorph of quartz.



a mineral that is one of the crystalline polymorphs of SiO2. Such trace elements as Fe, Al, and Na are commonly found in tridymite. It crystallizes in the form of colorless or gray tabular crystals, spherical aggregates, spear-shaped twins, and, often, trillings. It is a rare mineral and is usually encountered in cavities of juvenile extrusive acidic rocks and in tuffs; it is also found in meteorites and moon rocks. As a constituent of Dinas brick, tridymite determines the refractory properties of the brick.

References in periodicals archive ?
Fluxes decrease the temperature at which the silica starts to soften and provides liquid on the surface of the grains, increasing the reactivity and lowering the transition temperatures for tridymite and cristobalite.
It is believed this secondary expansion indicates the transformation of the silica from beta quartz to tridymite.
The X-ray powder diffraction patterns for the starting materials are shown in Figure 4, revealing high-intensity reflections attributed to quartz and kaolinite, although they also showed the presence of albite, crystoballite and tridymite.