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Other crystalline rocks, the metamorphic rocks such as marbles, mica-schists and quartzites, are recrystallized.This means that they were at first fragmental rocks like limestone, shale and sandstone and have never been in a molten condition nor entirely in solution, but the high temperature and pressure conditions of metamorphism have acted on them by erasing their original structures and inducing recrystallization in the solid state Specific industrial techniques to produce large single crystals (called boules) include the Czochralski process and the Bridgman technique.Garantie 24 de luni pentru toate apometrele vandute de compania noastra.
They can appear in glasses or polycrystals that have been made anisotropic by working or stress—for example, stress-induced birefringence.
One of the oldest techniques in the science of crystallography consists of measuring the three-dimensional orientations of the faces of a crystal, and using them to infer the underlying crystal symmetry. This is determined by the crystal structure (which restricts the possible facet orientations), the specific crystal chemistry and bonding (which may favor some facet types over others), and the conditions under which the crystal formed.