Quartzite (from German Quarzit)'s a hard metamorphic rock which was originally sandstone. Sandstone's converted into quartzite through heating and pressure usually related to tectonic compression within orogenic belts. Pure quartzite's usually white to grey, though quartzites often occur in various shades of pink and red due to varying amounts of iron oxide (Fe2O3). Other colors(Yellow, Orange) are commonly due to impurities of minor amounts of other minerals. When sandstone's metamorphosed to q… (More on Quartzite)