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.
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. The name quartzite implies not only a high degree of induration hardness , but also a high quartz content. Although a quartz-rich sandstone can look similar to quartzite, a fresh broken surface of quartzite will show breakage across quartz grains, whereas the sandstone will break around quartz grains.
Quartzite also tends to have a sugary appearance and glassy lustre. It breaks with a conchoidal fracture, which made it useful for tools with sharp edges, such as hoes, axes, and scrapers. Although it is very difficult to knap, some ancient people were able to knap it into knife blades and projectile points. The photo shows a quartzite arrowhead found in Alabama. If the arrowhead is turned under a bright light, the grains in the quartzite produce a sparkling luster. Quartzite has a diversity of uses in construction, manufacturing, architecture, and decorative arts.
Although its properties are superior to many currently used materials, its consumption has always been low for various reasons. The uses of quartzite and some reasons that it is avoided are summarized below. In architecture, marble and granite have been the favorite materials for thousands of years.
Quartzite, with a Mohs hardness of seven along with greater toughness, is superior to both in many uses. It stands up better to abrasion in stair treads, floor tiles, and countertops. It is more resistant to most chemicals and environmental conditions. It is available in a range of neutral colors that many people enjoy. The use of quartzite in these uses is growing slowly as more people learn about it.
There are also man-made materials marketed under the name quartzite. They can be attractive and durable with a cost comparable to natural materials. Read the marketing materials prepared by the manufacturer.
Quartzite can be an extremely durable crushed stone that is suitable for use in the most demanding applications. Its soundness and abrasion resistance are superior to most other materials. Unfortunately, the same durability that makes quartzite a superior construction material also limits its use.
Its hardness and toughness cause heavy wear on crushers, screens, truck beds, cutting tools, loaders, tires, tracks, drill bits, and other equipment. As a result, the use of quartzite is mainly limited to geographic areas where other aggregates are not available.
Quartzite is valued as a raw material because of its high silica content. These are mined and used to manufacture glass, ferrosilicon, manganese ferrosilicon, silicon metal, silicon carbide, and other materials. Quartzite can be a very attractive stone when it is colored by inclusions. Inclusions of fuchsite a green chromium-rich variety of muscovite mica can give quartzite a pleasing green color.
If the quartzite is semitransparent to translucent, the flat flakes of mica can reflect light to produce a glittering luster known as aventurescence.
Material that displays this property is known as " aventurine ," a popular material used to produce beads, cabochons, tumbled stones , and small ornaments. Aventurine can be pink or red when stained with iron. Included dumortierite produces a blue color.
Other inclusions produce white, gray, orange, or yellow aventurine. Quartzite has been used by humans to make stone tools for over one million years. It was mainly used for impact tools, but its conchoidal fracture allowed it to be broken to form sharp edges. Broken pieces of quartzite were used for crude cutting and chopping tools. Quartzite was not the preferred material for producing cutting tools such as knife blades and projectile points - but it has been used. Flint , chert , jasper, agate , and obsidian all can be knapped to produce fine cutting edges, which are difficult to produce when working quartzite.
Quartzite was most frequently used when it was locally abundant and superior materials were rare or not available. Article by: Hobart M. Find Other Topics on Geology. Maps Volcanoes World Maps. What Is Quartzite? Rock, Mineral and Fossil Collections. Hardness Picks. Flint, Chert, and Jasper. Tumbled Stones.
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