Metaquartzite – Anglesey

Metaquartzite is a hard, non-foliated metamorphic rock which was originally pure quartz sandstone which was converted into quartzite through the heat and pressure usually associated with tectonic 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 (Fe2O3). Other colors, such as yellow, green, blue and orange, are due to other mineral impurities.
The original individual quartz grains recrystallize along with the former cementing material to form an interlocking mosaic of quartz crystals. Most or all of the original texture and sedimentary structures of the sandstone are erased by the metamorphism The grainy, sandpaper-like surface becomes glassy in appearance. Minor amounts of former cementing materials, iron oxide, silica, carbonate and clay, often migrate during recrystallization and metamorphosis. This causes streaks and lenses to form within the quartzite. This example was collected near Holyhead on the Isle of Anglesey, North Wales, due to mineral impurities during formation, these samples have a pale green colouration to them as opposed to the Scottish material we supply, which is pure white. Specimens are supplied in labelled card trays and are available in various sizes.