Sandstone caves, multicoloured due to various oxides, containing carved tombs, historic and archaeological Nabataean city of Petra, UNESCO World Heritage Site, Jordan, Middle East

Sedimentary rocks, clay, colour banded by iron oxides, horizontal Triassic Chinle Clay, Blue Mesa, Painted Desert, Arizona, United States of America, North America

Yellow cake, powdery uranium oxide in Burwell filter press, Uranium City, Saskatchewan, Canada, North America

Indian petroglyphs drawn on red standstone by scratching away dark desert varnish of iron oxides, Newspaper Rock, Canyonlands, Utah, United States of America, North America

Petroglyphs carved 1000 years ago by Fremont Native American people in the iron oxide 'desert varnish' on the sandstone of Cub Creek Valley in this fossil park, Dinosaur National Monument, Utah, United States of America (USA), North America

Petroglyphs carved 1000 years ago by Fremont Native American people in the iron oxide 'desert varnish' on the sandstone of Cub Creek Valley in this fossil park, Dinosaur National Monument, Utah, United States of America (USA), North America

Petroglyph of male figure carved 1000 years ago by Fremont Native American people in the iron oxide 'desert varnish' on the sandstone of Cub Creek Valley in this fossil park, Dinosaur National Monument, Utah, United States of America (USA), North America

Iron oxide mine pollution, River Pelenna, Cwm Gwenffrwd, Tonmawr, Mid Glamorgan, Wales, Uk, Europe

Aerial view of red mud waste product in a holding pond from an aluminium production site near Stade, Lower Saxony, Germany

Aerial view of AOS bauxite loading wharf for aluminium production, site near Stade, Lower Saxony, Germany

Aerial view of AOS bauxite loading wharf for aluminium production, site near Stade, Lower Saxony, Germany

Green coloured rocks, discoloration caused by copper oxide, Marble Canyon, Arizona, USA

Stones coloured green by copper oxide, Marble Canyon, Arizona, USA

Plutonium button Plutonium metal button at Rocky Flats, CO. It consists on 98 percent plutonium and the rest other metals. Terri Coleman is the process specialist who is holding the button and using a brush to clean off oxide.

Monument Valley Navajo Tribal Park, Arizona, United States Of America

Monument Valley Navajo Tribal Park, Arizona, United States Of America

Tinto river, Huelva, Spain

Tinto river, Huelva, Spain

R?o Tinto, Andalucia, Spain *** Local Caption *** R?o Tinto ("Red River") is very acidic (Ph 2) and has a deep reddish hue due to iron dissolved in water. The acidity of the watercourse is linked to the drainage of pyrite, which is very present in the subsoil. Extremophilic and endemic bacteria and algae colonize the river bed, forming a fragile biofilm that evokes the hot springs of Yellowstone Park in the USA.

Clay loaded with iron oxides and dried out, Rio Tinto, Andalusia, Spain *** Local Caption *** R?o Tinto ("Red River") is very acidic (Ph 2) and has a deep reddish hue due to iron dissolved in water. The acidity of the watercourse is linked to the drainage of pyrite, which is very present in the subsoil. Extremophilic and endemic bacteria and algae colonize the river bed, forming a fragile biofilm that evokes the hot springs of Yellowstone Park in the USA.

R?o Tinto, Andalucia, Spain *** Local Caption *** R?o Tinto ("Red River") is very acidic (Ph 2) and has a deep reddish hue due to iron dissolved in water. The acidity of the watercourse is linked to the drainage of pyrite, which is very present in the subsoil. Extremophilic and endemic bacteria and algae colonize the river bed, forming a fragile biofilm that evokes the hot springs of Yellowstone Park in the USA.

Reflection of trees in Tinto river, Rio Tinto minas, Rio Tinto, Huelva, Spain