Quartzite
Quartzite is a metamorphic rock derived from sandstone that is distinguished from sandstone by its fracture. Sandstone breaks along grain boundaries, whereas quartzite is so well indurated (hardened) that it breaks across constituent grains. The intense heat and pressure of metamorphism causes the quartz grains to compact and become tightly intergrown with each other, resulting in very hard and dense quartzite.
Type
Rock
Color
Usually white or gray, can be other colors, due to impurities.
Description
Quartzite is a metamorphic rock derived from sandstone that is distinguished from sandstone by its fracture. Sandstone breaks along grain boundaries, whereas quartzite is so well indurated (hardened) that it breaks across constituent grains. The intense heat and pressure of metamorphism causes the quartz grains to compact and become tightly intergrown with each other, resulting in very hard and dense quartzite.
Relation to Mining
Because it is so dense and resistant to both physical and chemical weathering, it is a poor bedrock on which to form soil. As a result, typically-quarried quartzite is very near the surface. Because it is so hard and dense, quartzite has not been quarried as extensively as other softer dimension stone (such as limestone, sandstone and granite).
Uses
Since quartzite breaks into flat surfaces, it is used as a dimension stone in the construction industry, for decorative stone in building construction and for some aggregates.