Claudio Contreras / Hierve el Agua rock formation with calcified minerals, resembling a waterfall. Oaxaca, southern Mexico.

David Fleetham / Red encrusting sponge (Clathria sp) on calcium carbonate-producing Seaweed / Green algae (Halimeda kanaloana). Hawaii.

Floris van Breugel / Tufa towers along Mono Lake, which form as sodium carbonate reacts with calcium rich spring water. Mono Lake, California, USA. June 2017.

Floris van Breugel / Tufa towers along Mono Lake, which form as sodium carbonate reacts with calcium rich spring water. Mono Lake, California, USA. September.

Floris van Breugel / Tufa towers along Mono Lake, which form as sodium carbonate reacts with calcium rich spring water. Mono Lake, California, USA. June 2017.

Philippe Clement / Dolomite specimen, anhydrous carbonate mineral composed of calcium magnesium carbonate on white background

Alex Hyde / Straw or tubular stalactites which are very delicate, hollow structures. They form when calcium carbonate or calcium sulfate dissolved in the water comes out of solution and is deposited in a ring aro...

Alex Hyde / Close up of straw or tubular Stalactites which are very delicate, hollow structures. They form when calcium carbonate or calcium sulphate dissolved in the water, deposited in a ring around the outsid...

Alex Hyde / Close up of straw or tubular stalactite, a very delicate, hollow structure. They form when calcium carbonate or calcium sulfate dissolved in the water is deposited in a ring around the outside of each...

John Cancalosi / Chalk, calcium carbonate or CaCO3 from Rotting Dean, England, UK.

Mark Taylor / Calcium carbonate covered plants in hot spring, Yellowstone National Park, Wyoming, USA

Mark Taylor / Calcium carbonate covered plants in hot spring, Yellowstone National Park, Wyoming, USA

Jack Dykinga / Dawn at Inspiration Point, with calcium carbonate hoodoo formations glowing, Bryce Canyon National Park, Utah, USA

David Maitland / Cross section through Spine of Sea Urchin (Echinus lividus) shows how its entire structure is made up from a repeating “building-block” pattern of calcium carbonate plates arranged radially in a symme...

Steven David Miller / Ngilgi Cave is in a system of limestone caves richly decorated with the calcium carbonate formations including this stalactite tipped with a cluster of crystals. The clear straw at the base is man-ma...

Steven David Miller / Ngilgi Cave is in a system of limestone caves richly decorated with the calcium carbonate formations including flowstone. Leeuwin-Naturaliste National Park, Southwest Western Australia

Steven David Miller / Ngilgi Cave is in a system of limestone caves richly decorated with the calcium carbonate formations including flowstone. Leeuwin-Naturaliste National Park, Southwest Western Australia

Steven David Miller / Ngilgi Cave is in a system of limestone caves richly decorated with the calcium carbonate formations including flowstone. Leeuwin-Naturaliste National Park, Southwest Western Australia

Steven David Miller / Ngilgi Cave, a limestone cave richly decorated with the calcium carbonate formations including flowstone resembling shawls or slabs of bacon. Leeuwin-Naturaliste National Park, Southwest Western Aus...

Thomas Lazar / Morning light on calcium carbonate Tufa towers in mineral rice lake waters, Mono Basin National Forest Scenic Area, INYO National Forest, California, USA, June 2008

Philippe Clement / Tubes of of calcium carbonate from a serpulid worm attached to shell on beach, Brittany, France

Philippe Clement / Tubes of of calcium carbonate from a serpulid worm attached to mollusc shell, Brittany, France

Juergen Freund / Shell / test of a Foraminifer (or "Foram"), an important source of calcium carbonate in marine sediments and sedimentary rocks

Juergen Freund / Blocks of soft coquina limestone formed from shells of Bivalve Cardiid Cockle {Fragrum erugatum} Rainwater repeatedly dissolves small quantities of calcium carbonate of which the shells are composed....

Adrian Davies / Tufa towers, Mono Lake, California, USA

Adrian Davies / Tufa towers, Mono Lake, California, USA

Adrian Davies / Tufa towers, Mono Lake, California, USA

John Cancalosi / Calcium carbonate rock Sahara desert Morocco

Constantinos Petrinos / Bleached soft leather coral {Sinularia sp} Sulawesi Indonesia. Temperature change results in loss of symbiotic zooxanthellae from tissues of polyps, this exposes white calcium carbonate skeleton.

Doug Wechsler / Tufa towers of calcium carbonate formed by alkaline spring water. Mono Lake, California, USA

Heidi & Hans-Juergen Koch / Edible Snail (Helix pomatia) pair with love dart between them, a calcium carbonate organ used to stimulate the partner during courtship, Aardenburg, Netherlands

John Cancalosi / Calcite (Ca CO3, calcium carbonate), one of the most common and variable minerals on earth, used in building, metallugy, fertilizers, chemical industry, with pyrite and marcasite. Sample from Conco Mi...

John Cancalosi / Calcite, (CaCO3, calcium carbonate), one of the most common and variable minerals on earth, used in building, metallugy, fertilizers, chemical industry. Sample from Sweetwater mine, Viburnum trend, Mi...

John Cancalosi / Calcite (Ca CO3, calcium carbonate), one of the most common and variable minerals on earth, used in building, metallugy, fertilizers, chemical industry, with pyrite and marcasite. Sample from Conco Mi...

John Cancalosi / Calcite, (CaCO3, calcium carbonate), one of the most common and variable minerals on earth, used in building, metallugy, fertilizers, chemical industry, also with some chalcopyrite (iridescent). Sampl...

John Cancalosi / Calcite (Ca CO3, calcium carbonate), one of the most common and variable minerals on earth, used in building, metallugy, fertilizers, chemical industry, with pyrite and marcasite. Sample from Conco Mi...

John Cancalosi / Calcite crystal (CaCO3, calcium carbonate) covered with siderite (FeCO3, iron carbonate). Drouba Mine, Rhodopi Mountains, Bulgaria

John Cancalosi / Calcite (Calcium carbonate, CaCO3). One of the most common and variable minerals on earth, used in building, metallugy, fertilisers and the chemical industry. Juchem Quarry, Idar-Oberstein, Hunsruck M...

John Cancalosi / Calcite (Calcium carbonate, CaCO3) with haematite inclusions causing red colour. One of the most common and variable minerals on earth, used in building, metallugy, fertilisers and the chemical indust...

John Cancalosi / Calcite (Calcium carbonate, CaCO3). One of the most common and variable minerals on earth, used in building, metallugy, fertilisers and the chemical industry. Auglaize Quarry, Junction, Ohio. USA

John Cancalosi / Aragonite crystals (Ca CO3 / Calcium carbonate) from China

John Cancalosi / Calcite crystal on Amethyst. Calcite [Ca Co3 / Calcium Carbonate] one of the most common minerals on Earth. Amethyst [Sio2 / Silicon dioxide] a form of Quartz, the most common mineral on Earth

Graham Eaton / Aragonite, calcium carbonate, CaCO3, from the Yorkshire Dales, UK

Doug Wechsler / Kidney Stone made of calcium oxalate, Pennsylvania, USA.

Milan Radisics / Aerial view of ash pond near Turek, Poland. Former open pit coal mine now used to store coal ash after burning in power plants. The ash is mixed with water and pumped through a pipeline into the ash p...

Milan Radisics / Aerial view of ash pond near Turek, Poland. Former open pit coal mine now used to store coal ash after burning in power plants. The ash is mixed with water and pumped through a pipeline into the ash p...

Milan Radisics / Aerial view of ash pond near Turek, Poland. Former open pit coal mine now used to store coal ash after burning in power plants. The ash is mixed with water and pumped through a pipeline into the ash p...

Milan Radisics / Aerial view of ash pond near Turek, Poland. Former open pit coal mine now used to store coal ash after burning in power plants. The ash is mixed with water and pumped through a pipeline into the ash p...

Milan Radisics / Aerial view of ash pond near Turek, Poland. Former open pit coal mine now used to store coal ash after burning in power plants. The ash is mixed with water and pumped through a pipeline into the ash p...

Milan Radisics / Aerial view of ash pond near Turek, Poland. Former open pit coal mine now used to store coal ash after burning in power plants. The ash is mixed with water and pumped through a pipeline into the ash p...

Milan Radisics / Aerial view of ash pond near Turek, Poland. Former open pit coal mine now used to store coal ash after burning in power plants. The ash is mixed with water and pumped through pipelines (fixed on sand...