Quartzite is a hard, non-foliated metamorphic rock which was originally pure quartz sandstone.Sandstone is converted into quartzite through heating and pressure usually related totectonic compression within orogenic belts. Pure quartzite is usually white to grey, though quartzites often occur in various shades of pink and red due to varying amounts of iron oxide. Other colours, such as yellow, green, blue and orange, are due to other mineral impurities. The metamorphism causes the recrystallization and the merger of the grains that formed the sandstone, giving rise to a very compact rock, hard and quite rough to the touch. Despite being a metamorphic rock, sometimes it preserves the remains of fuels, as well as crustaceans (footprint fossils of marine arthropods).