quartzite

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quartzite A metamorphic rock composed mainly of quartz and usually formed by the metamorphism of quartz sandstones. If deformation has accompanied metamorphism the individual quartz crystals are elongate and take on a preferred orientation, defining a planar or linear fabric within the rock. Unmetamorphosed sedimentary quartzites (sandstones with a quartz cement) are known as ‘orthoquartzites’ to distinguish them from metamorphic quartzites (metaquartzites).

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quartzite, usually metamorphic rock composed of firmly cemented quartz grains. Most often it is white, light gray, yellowish, or light brown, but is sometimes colored blue, green, purple, or black by included minerals. It results from the metamorphism of pure quartz sandstone. It is most easily distinguished from sandstone by the fact that it fractures across its constituent grains of sand, while sandstone fractures along the line of the cementing material between the grains of sand. Although most quartzites are metamorphic, some are sedimentary in origin, resulting from cementation of quartz sandstone by groundwater solutions containing pure quartz.

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quartzite Metamorphic rock usually produced from sandstone, in which the quartz grains have recrystallized. Quartzite is a hard and massive rock. It is usually white, light grey, yellow or buff, but it can be coloured green, blue, purple, or black by various minerals.