Quartzite is a metamorphic rock that forms when sandstone is heated under pressure deep within the Earth and should not be confused with mineral quartz. When quartzite is pure is most often white or greyish. Quartzite can be reddish or pinkish if iron oxide is present. Different mineral impurities can give quartzite different colours. Fossils are rare in quartzite. Quartzite resists chemical weathering and therefore forms ridges and hilltops when less resistant rocks round it have eroded away. Quartzite does not form good soils therefore quartzite ridges are likely to be bare or to have poor soil and sparse vegetation.