Quartzite

Background |  Name |   Sources |  Uses |  Substitutes and Alternative Sources

Background

Quartzite is a nonfoliated metamorphic rock that formed by the metamorphism of pure quartz sandstone. 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. Quartzite is usually white or gray, but can be other light colors depending on the impurities in the parent sandstone. It has a glassy luster, as would be expected considering the quartz in sandstone has a vitreous or glassy luster. When quartzite weathers it can have a granular appearance, but freshly broken surfaces break in even surfaces because the break goes through the intergrown quartz grains. (By comparison, sandstone breaks around the quartz grains and therefore shows a granular appearance on a freshly broken surface.) They can form anywhere heat and pressure change pre-existing sandstone deposits, so quartzite is found both in geologic settings of regional metamorphism (where metamorphism occurs more from pressure than heat) and contact metamorphism (where metamorphism occurs more from heat than pressure). However, quartzite most typically forms during mountain-building events where continents collide with each other. Because it is so dense and tough, quartzite is extremely resistant to weathering and erosion.

Name

Geologically speaking quartzite occurs in regions of regional, high-pressure metamorphism. In the United States quartzite quarries are found in Idaho, New York, Wisconsin, Pennsylvania, Minnesota, Montana, Arizona and South Dakota. Because it is so dense and resistant to both physical and chemical weathering, it is 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), although construction industry experts estimate that present demand exceeds annual production.

A total of 1.3 billion tons of crushed rock is produced in the United States annually. Of this, less than 6% is quartzite. In fact, sandstone, marble, scoria, volcanic cinder and miscellaneous stone - all together - account for less than 6% of the total crushed stone production in the U.S.

Uses

Quartzite is becoming more popular as a dimension stone in the construction industry. The use of quartzite as decorative stone in building construction is growing annually. As noted above, quartzite breaks into flat surfaces. Consequently, quartzite slabs are used to cover walls, as roofing tiles, as flooring, and stair steps to name just a few applications.
Quartzite is also used, to a small degree, as crushed stone. The vast majority of crushed stone - about 85% - is used in road construction and repair. In the United States, most crushed stone produced is limestone, granite, and trap rock. Limestone represents 70% of all the crushed rock produced.

Substitutes and Alternative Sources

Other hard, durable rock types are used in road construction and repair. Since they are extremely plentiful and easier to quarry than quartzite, it is not likely that quartzite will be utilized in greater amounts as a crushed rock. On occasion, quartzite is the alternative to other crushed rock simply because it is locally available.
The popularity of quartzite as dimension stone in construction is growing dramatically each year . It is an interesting rock with great durability and a unique texture. More and more contractors and homeowners are using quartzite to finish and decorate their buildings. Natural alternative materials include sandstone, granite, and marble. Created materials include bricks, ceramic tiles, concrete, plastics, and resin-agglomerated stone. (“Resin-agglomerated stone” is a material composed of crushed pieces of stone held together by resin, then cut to the dimensions and shapes needed for each application) There are other materials readily available that have very different physical characteristics. Two examples are aluminum and steel.

 

By Darryl Powell

Darryl Powell is a 1984 graduate of the University of Rochester, Rochester, New York with a B.S. in Geological Sciences. For six years Mr. Powell was an Adjunct Professor at Finger Lakes Community College in Canandaigua, New York, where he taught “Introduction to Physical and Historical Geology.” He creates Earth Science educational kits for NeoSCI, Inc., a science education resource company based in Rochester, New York. He also writes Earth Science materials for NewPath Learning, Inc. based in Victor, New York. Mr. Powell is the founder of Diamond Dan Publications, a small company focused on creative activity books and activity-based learning games about rocks and minerals, based in Manchester, New York.