Rod Williams / Hoverfly (Helophilus pendulus) Lewisham, London, August

Guy Edwardes / Dawn mist around Hambledon Hill from Bullbarrow Hill, Cranbourne Chase, Dorset, England, UK. February 2016.

Eric Baccega / Dallol hot spring with salt concretions coloured by sulphur, potassium and iron, Dallol Volcano, Danakil Depression, Ethiopia, March 2015.

Eric Baccega / Dallol hot spring with salt concretions coloured by sulphur, potassium and iron, Dallol Volcano, Danakil Depression, Ethiopia, March 2015.

Eric Baccega / Dallol hot spring with salt concretions coloured by sulphur, potassium and iron, Dallol Volcano, Danakil Depression, Ethiopia, March 2015.

Pascal Kobeh / Giant clam (Tridacna) on 'Lotus' artificial reef, built in 2001 with a steel frame using mild electric currents to encourage coral growth, with diver in the background. Vabbinfaru Island in North Male...

Aflo / Stray cats, on black and one tabby, peering out of hole in rusty corrugated iron. Chiyoboinari Shrine, Kaizu, Japan.

Sergey Gorshkov / Snow goose (Chen caerulescens caerulescens) brooding chicks, with rusty orange face from iron rich soil in which it forages. Wrangel Island, Far Eastern Russia, June.

Dr. Axel Gebauer / Bacteria - iron and manganese oxidizers and their complementary reducers, in the mud of an empty fish pond, Upper Lusatia Heath and Pond Landscape, Upper Lusatia UNESCO Biosphere Reserve, Germany

Jurgen Freund / Aerial of Sturt Stoney Desert with gibber rocks. Gibber rocks are millions of years wind and water weathered chalcedonised sandstone with a hardened crust of soil cemented silica, iron and manganese,...

Luke Massey / 2020VISION / Two Turtle doves (Streptopelia turtur) perched on a rusting iron rail in a rain shower, Essex, England, UK, June.

Luke Massey / 2020VISION / Little owl (Athene noctua) perched on a rusting iron wheel, Essex, England, UK, June.

Luke Massey / 2020VISION / Little owl (Athene noctua) perched on a rusting iron wheel, Essex, England, UK, June.

Juan Carlos Munoz / Red waters of the Rio Tinto, coloured by dissolved minerals, primarily iron. Andalusia, Spain, December 2011.

Juan Carlos Munoz / Red waters of the Rio Tinto, coloured by dissolved minerals, primarily iron. Andalusia, Spain, December 2011.

Juan Carlos Munoz / Red waters of the Rio Tinto, coloured by dissolved minerals, primarily iron. Andalusia, Spain, December 2011.

Juan Carlos Munoz / Red waters of the Rio Tinto, coloured by dissolved minerals, primarily iron. Andalusia, Spain, December 2011.

Juan Carlos Munoz / Red waters of the Rio Tinto, coloured by dissolved minerals, primarily iron. Andalusia, Spain, December 2011.

Konrad Wothe / Magnificent riflebird (Ptiloris magnificus) male perched in rainforest, Iron Range National Park, Cape York Peninsula, North Queensland, Australia, November

Konrad Wothe / Common green tree frog (Litoria caerulea) in rainforest, Iron Range National Park, Cape York Peninsula, North Queensland, Australia, October

John Cancalosi / Staurolite (iron aluminum silicate hydroxide), always crystallized often with two indivuals intergrown at right angles forming a cross. Sometimes used as amulets or ornaments. A fairly common metamorh...

John Cancalosi / Pyrite (FeS2, iron sulfide), known as 'Fool's Gold'. Formerly used in the production of sulfuric acid. Sample from Concepcion de Oro, Zacatecas State, Mexico.

Graham Brazendale / "HMS Warrior" berthed at Historic Naval Dockyard, with small boats anchored alongside. Portsmouth, England, July 2010. Non-editorial uses must be cleared individually.

Chadden Hunter / Dallol hot springs where water heated by magma laden with potassium, sulphur and iron spews up through salt pans staining the salt deposits with vivid colours, in the bottom of the Rift Valley, 120 me...

Luiz Claudio Marigo / Turtle Rock, created by erosion in Sete Cidades National Park, municipality of Piracuruca, Piaua­ State, Northeastern Brazil. Darkening of the rock is due to the iron oxide. March 2009

Angelo Gandolfi / Las Medulas, Cordillera Cantabrica, Castilla y Leon, Spain. The landscape, now a natural reserve, is man-made: the rock formations are the result of iron mining since Roman times and the wood is culti...

Jack Dykinga / Concretion balls lining fracture lines in petrified sand dune formation, with lichen scaring calcification marks, Colorado Plateau, Arizona, USA

Wild Wonders of Europe / Smit / River Danube flowing through the Iron Gate Gorge, on the border between Romania and Serbia, Djerdap National Park, Serbia, June 2009

Wild Wonders of Europe / Smit / Photographer, Ruben Smit, above the River Danube flowing through the Iron Gate Gorge, on the border between Romania and Serbia, Djerdap National Park, Serbia, June 2009

Wild Wonders of Europe / Smit / Low clouds over the River Danube flowing through the Iron Gate Gorge, Djerdap National Park, Serbia, June 2009 WWE BOOK PLATE.

Guy Edwardes / Tre'r Ceiri Iron Age hill fort, Yr Eifl, looking towards the Menai Straits, Lleyn peninsula, Gwynedd, Wales, UK, December 2008

Jose B. Ruiz / Fig leaf in water from the Río Tinto, or Red River, very acidic and coloured deep red by iron dissolved in the water that drains from the local Riotinto mines causing severe environmental problems. Hu...

Jose B. Ruiz / Dead Libellula dragonfly in the Rio Tinto, or Red River, very acidic and coloured deep red by iron dissolved in the water, causing severe environmental problems. Huelva, Spain

Jose B. Ruiz / Río Tinto, or Red River, very acidic and coloured deep red by iron dissolved in the water that drains from the local Riotinto mines causing severe environmental problems. Huelva, Spain .

Flip Nicklin / Bearded Seal (Erignathus barbatus) male resting on ice floe with head dyed red from the high iron content of ocean mud in which he hunts for shrimp and clams, Svalbard, arctic Norway

Flip Nicklin / Bearded Seal (Erignathus barbatus) with head stained red from iron-rich soil sediments in which it forages for food, Svalbard, Norway

Steve Nicholls / Seeds of Rough hawkbit (Leontodon hispidus) studio shot, composite image, collected from Iron Mill Common, Gloucestershire, England, UK. September.

Philippe Clement / Levee / dyke and Nieuwe Sluis, lighthouse near Breskens which marks the entrance to the Western Scheldt / Westerschelde, Zeeland, the Netherlands, February 2019

Philippe Clement / Tourist visiting Mousa Broch, tallest Iron Age broch and one of Europe's best-preserved prehistoric buildings, Shetland Islands, Scotland, UK. June 2018. Digital composite

Adrian Davies / Ancient cave paintings, painted with iron oxide (ochre). Cueva de Los Letreros, Almeria Spain. Approx. 5,000 years old.

Nigel Cattlin / Iron deficiency symptoms with interveinal chlorosis on cultivated Bougainvillea (Bougainvillea sp) leaves.

Nigel Cattlin / Iron deficiency symptoms with interveinal chlorosis on cultivated Bougainvillea (Bougainvillea sp) leaves.

John Cancalosi / Polished Sonora sunrise rock slab, composed of chrysocolla, cuprite and iron. From Milpillas Mine, Cuitata, Municipio de Cananea, Sonora, Mexico.

Nigel Cattlin / Apple (Malus domestica) branch with fruits and leaves. Leaves exhibiting interveinal chlorosis, symptom of iron deficiency.

Nigel Cattlin / Apple (Malus domestica) tree leaves with interveinal chlorosis, symptom of iron deficiency.

Michel Roggo / Meander of Rio Tinto, an acidic river with high iron levels resulting in red and orange colours. Aerial view. Photographed for The Freshwater Project extended. Andalucia, Spain. April 2019.

Michel Roggo / Meander of Rio Tinto, an acidic river with high iron levels resulting in red and orange colours. Aerial view. Photographed for The Freshwater Project extended. Andalucia, Spain. April 2019.

Michel Roggo / Aerial view of Rio Tinto, an acidic river with high iron levels resulting in red and orange colours. Photographed for The Freshwater Project extended. Andalucia, Spain. April 2019.

Michel Roggo / Aerial view of Rio Tinto, an acidic river with high iron levels resulting in red and orange colours. Photographed for The Freshwater Project extended. Andalucia, Spain. April 2019.