A high-temperature form of quartz found as thin hexagonal crystals in some igneous rocks and stony meteorites.
- ‘Although the optical, SEM, and XRD data are consistent with quartz, considering the incongruous crystal symmetry, it is likely that this mineral is actually a quartz pseudomorph after tridymite.’
- ‘The abundant and ubiquitous quartz paramorphs after tridymite in the walls attest to a very shallow emplacement depth.’
- ‘Quartz paramorphs after tridymite are absent from Fiachanis but present in the three Priomh-lochs samples adjacent to late minor intrusions.’
- ‘Because there is a significant difference in crystal structure among the three forms, cooling tridymite or crystoballite below 572°F results in metastable forms that retain the high temperature structure.’
Mid 19th century from German Tridymit, from Greek tridumos ‘threefold’, from tri- ‘three’ + -dumos (as in didumos ‘twin’), because of its occurrence in groups of three crystals.