Quartzite is an extremely hard metamorphic rock which was originally pure quartz sandstone. Sandstone is converted into quartzite through heating and pressure usually related to tectonic compression within orogenic belts.
Minerals such as iron oxide, silica and carbonate crystalize during the metamorphosis resulting in a glassy appearance when polished. This gives quartzite a soft marble like look but has the durability of granite. Even though quartzite is an extremely dense material, it is slightly absorbent so should be sealed for use as a countertop.