What is quartzite?

How does quartzite form?

Quartzite starts as sandstone. When quartz-rich sandstone is buried deep and exposed to heat, pressure and chemically active fluids, the sand grains and silica cement recrystallize into a tight, interlocking quartz network. Most quartzite forms during mountain building at convergent plate boundaries.

That interlocking structure makes the rock tough. When it breaks, the fracture runs through the quartz grains rather than around them, which is how geologists tell it from sandstone. It is also why quartzite often survives as ridges after softer rock around it erodes.

Is soft quartzite a real type of stone?

No. Quartz is 7 on the Mohs scale, harder than glass or a knife blade, so true quartzite is hard by definition. A slab described as soft quartzite is most likely marble, and the name tends to excuse a stone that etches or scratches.

Mislabeling is common because the two can look alike and name, price and country of origin do not prove which you have. Super White is usually dolomitic marble. Fantasy Brown is described as a dolomitic marble with quartzite characteristics, so it is harder than typical marble but softer than true quartzite.

How can you tell if a slab is real quartzite?

Run more than one test on a sample, because any single test can mislead. None of these is a lab analysis, and a stone supplier can provide the geology for a given slab.

Does quartzite need to be sealed?

Usually, yes. Quartzite is porous, though less than marble, and porosity varies by stone. Dense varieties like Taj Mahal and Sea Pearl are commonly sealed every 12 to 18 months, while more porous ones such as Fantasy Brown may need it every 6 to 12 months.

Run the water test: if a drop soaks in and darkens the stone within about 10 minutes, reseal. Use an impregnating sealer, as described in how to seal marble.

Where is quartzite used?

Its hardness and toughness make quartzite suitable for countertops, stair treads and floor tile, though it is used less than marble and granite. Crushed quartzite is a durable aggregate but wears equipment heavily. High-silica deposits go into glass and silicon manufacturing, and people have shaped it into stone tools for over a million years.

For bathrooms it appears mainly as vanity tops, wall cladding and floors. The slabs are harder to cut than marble, which affects fabrication cost; see quartzite vs marble and quartzite vs granite.

What colors and varieties does quartzite come in?

Quartzite is usually white to gray, with iron staining giving pink, red or purple, and other impurities producing yellow, orange, brown, green or blue. Fuchsite inclusions give a green cast, and mica flakes can create a glittering effect. Trade names matter more than color when you shop, because porosity, price and even identity vary by name.

Does Pietra Fonte use quartzite?

No. Pietra Fonte makes solid natural-stone bathtubs, basins and vanities to order, each carved from a single block of marble, travertine, onyx and other stones. We do not offer quartzite, quartz or granite pieces. See marble, travertine and onyx.