Quartzite

The metamorphic rock quartzite is formed from sandstone or chert that has been heated and recrystallized during metamorphic episodes such as regional deformation or contact with molten rock. Exposed quartzites are resistant to weathering and commonly project as high hills and ridges.

Some of the textural features of the original sandstone or chert, such as the shape and size of the grains and the type of bedding, are retained. Quartzite derived from sandstone shows dust-like inclusions that can show the outlines of the original grains. Quartzite from impure sandstones (Containing mica or feldspar) may grade into other metamorphic rocks, such as schist or gniess. A mosaic of small grains is typical of quatzite derived from chert. If the chert had altering thin layers of silica and shaley material, the quartzite typically preserves this feature. Quartzite formed during regional deformation shows the pressure or stress of metamorphism in elongated and parallel quartz grains or in a preferred orientation of the crystallographic axes of quartz grains of any shape.