What is Quartzite?

A natural stone with a marble look and the toughness of granite.

Not to be confused with manmade quartz, quartzite is 100% natural and comes directly from the earth. Quartzite has formed in locations all around the planet and the most well-known quartzite quarries are in Brazil. Quartzite is also quarried in the United States, Sweden, Canada, Norway, India, and Italy, among other locales.

It’s a metamorphic rock – one that’s been baked into an extra-tough stone by the heat and pressure that only comes from deep burial way down in Earth’s crust. Such events are usually brought about by tectonic collisions, where continents grind into each other. 

Quartzite isn’t melted sandstone. It’s sandstone that is fused together so tightly that the sand grains lose their individual identities. The minerals crystallize together into a dense fabric of quartz crystals. The deeper and hotter the stone gets, the more tightly it’s fused. 

Here is the key point: The heat and pressure that turn sandstone to quartzite is not a definitive, black-and-white occurrence. It’s a gradual process, with subtle differences occurring all along the spectrum. There is no exact moment that sandstone becomes quartzite. It’s similar to the way that colors blend from one shade to the next. When does Royal Blue become Navy Blue? It’s hard to pin down, exactly. Because there is a range of quartzites and sandstones, it’s wise to assess each stone as an individual, rather than relying on broad categories or stone names as the last word on how a given stone will behave. 

The geological process – Quartzite is first deposited as beach sand, and then buried and compressed into solid rock to make sandstone. Then the stone was pushed deeper into Earth’s crust where it was further and compressed and heated into a metamorphic rock. During metamorphism, quartzite experiences temperatures somewhere between 800° and 3000° F, and pressures of at least 40,000 pounds per square inch (in metric units, that’s 400° to 1600° C and 300 MPa), all over the course of millions of years. 

Natural quartzites are not all alike. There is variation in how deeply they were buried and for how long, and what types of conditions they endured. Because of this, some quartzites are somewhat porous (like Macaubas), while others are tightly bonded together (like Marine Blue, Taj Mahal, or Fusion).   

It’s Applications – Natural quartzite is at home in many applications, from countertops and flooring, to outdoor kitchens and cladding. Harsh weather and UV light won’t affect the stone.   

The most common problem with quartzites is inadequate sealing – particularly along the edges and cut surfaces. As described above, some quartzites are porous and care must be taken to seal the stone. When in doubt, be sure to work with a fabricator who is experienced with the particular quartzite you are considering.