Rock facts, water nasties and ‘desire lines’
QIt’s easy to spot rocks of different colours around the mountains, but what gives them their different shades?
Paul says The colour of a rock is dependent on the minerals it’s made up of. Rocks originating in the earth’s mantle (such as olivine) are often greenish in colour. However, when a rock is exposed to the atmosphere it is chemically ‘weathered’ and often changes colour. Reddish colouring, for example, is often due to oxidisation (rusting) of iron minerals on the rock’s surface. There is a general trend for rocks to become some shade of grey as they weather, but there are always exceptions and varieties of colour.