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Quartz is, therefore, classified structurally as a framework silicate mineral and compositionally as an oxide mineral. Quartz is the second most abundant mineral in Earth's continental crust, behind feldspar. [10] Quartz exists in two forms, the normal α-quartz and the high-temperature β-quartz, both of which are chiral. The transformation ...
The room-temperature form of quartz, α-quartz, undergoes a reversible change in crystal structure at 573 °C to form β-quartz.This phenomenon is called an inversion, and for the α to β quartz inversion is accompanied by a linear expansion of 0.45%.
In particular, there are crystals that have trigonal symmetry but belong to the hexagonal lattice (such as α-quartz). The hexagonal crystal family consists of the 12 point groups such that at least one of their space groups has the hexagonal lattice as underlying lattice, and is the union of the hexagonal crystal system and the trigonal ...
Alpha quartz is the most stable form of solid SiO 2 at room temperature. The high-temperature minerals, cristobalite and tridymite, have both lower densities and indices of refraction than quartz. The transformation from α-quartz to beta-quartz takes place abruptly at 573 °C.
Quartz is one of the several crystalline forms of silica, SiO 2. The most important forms of silica include: α-quartz, β-quartz, tridymite, cristobalite, coesite, and stishovite. Polymorphism is the occurrence of multiple crystalline forms of a material. It is found in many crystalline materials including polymers, minerals, and metals ...
English: This figure illustrates the chiral crystal structure of alpha-quartz along a, b, and c directions. The space group P3_121 and P3_221 are an enantiomorphic pair. Red balls represent oxygen atoms and blue balls represent silicon ato
Thermal diffusivity is usually denoted by lowercase alpha ... Quartz: 1.4 [15] Sandstone 1.15 Ice at 0 °C 1.02 Silicon dioxide (polycrystalline) 0.83 [15]
Cristobalite is stable only above 1470 °C, but can crystallize and persist metastably at lower temperatures. The persistence of cristobalite outside its thermodynamic stability range occurs because the transition from cristobalite to quartz or tridymite is "reconstructive", requiring the breaking up and reforming of the silica framework.