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...

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

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

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.

Graham Eaton / Disused copper mine and quarry workings, Parys Mountain, Amlwch, Isle of Anglesey, Wales, UK, September 2016.

Jen Guyton / 'Singing rocks' which make a resonating clang when banged together because of their high iron content. Namib Desert, Namibia

John Cancalosi / Botryoidal hematite main ore mineral of iron, Morocco

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

Pal Hermansen / Svalbard Global Seed Vault, with glittering facade designed by artist Dyveke Sanne. Light reflected in steel, mirrors, and prisms in landscape, Svalbard, Norway, October 2012.

Pal Hermansen / Moon and glittering facade designed by artist Dyveke Sanne, on the roof of the Svalbard Global Seed Vault. Light reflected in steel, mirrors, and prisms in landscape, Svalbard, Norway, October 2012

Pal Hermansen / Svalbard Global Seed Vault, with glittering facade designed by artist Dyveke Sanne., on the roof of the Svalbard Global Seed Vault. Light reflected in steel, mirrors, and prisms in landscape, Svalbard...

John Waters / Cast iron figure by sculptor Anthony Gormley from his series called "6 Times", located along Water of Leith, Edinburgh, Scotland, UK. June. Editorial use only

Guy Edwardes / Whiteford Point Lighthouse, derelict 1865 cast-iron lighthouse, Whiteford Point, Gower Peninsula, Wales, UK. August.

Ashley Cooper / Photovoltaic panel on side of house. Near Puerto Natales, Magallanes, Chile. January 2020.

Philippe Clement / Strunzite, phosphate triclinic-pinacoidal mineral containing hydrogen, iron, manganese, oxygen, and phosphorus against white background