Floris van Breugel / A rock collector explores piles of fluorescent minerals found in the tailings of the Pacific Tungsten Mine near Darwin, California. The bright colours are caused by fluorescence excited by a shortwave...

Andrew Cooper / Calcite vein between grass. Dartmoor National Park, UK, June.

Philippe Clement / Rounded nodules on the beach near Osmington Mills, made of calcite-cemented sandstone from the Bencliff Grit Formation along the World Heritage Site Jurassic Coast, Dorset, UK, November 2012

Philippe Clement / Rounded nodules on the beach near Osmington Mills, made of calcite-cemented sandstone from the Bencliff Grit Formation along the World Heritage Site Jurassic Coast, Dorset, UK, November 2012

Floris van Breugel / A wide variety of fluorescent minerals including scheelite (blue/white), calcite (red), silica coatings containing uranyl ions (green), fluorite (pink), and 'desert varnish' (yellow/orange), populate...

Jean E. Roche / Calcite and Aragonite deposits in the Clamouse caves, Herault, Languedoc, France, August 2008

Robert Thompson / Calcite cradle and stalactites in the Marble Arch Caves, County Fermanagh, Northern Ireland, UK, January 1995

George Sanker / Calcite Overlook, formed by the Yellowstone River, after a thunderstorm at sunset, Yellowstone National Park, Wyoming, USA, June 2008

John Cancalosi / Willemite (green) and Calcite (red) taken under UV light, Franklin, New Jersey, USA

John Cancalosi / Willemite (red) and Calcite (white) taken under normal light, Franklin, New Jersey, USA

John Cancalosi / Fluorescent minerals, Willemite (green) and Calcite (red), Sterling Mine, New Jersey, USA

John Cancalosi / Fluorescent minerals, Willemite (green) and Calcite (red), Sterling Mine, New Jersey, USA

John Cancalosi / Fluorescent Minerals, Willemite (green) and Calcite (red), Sterling Mine, New Jersey, USA

Ingo Arndt / Calcite flowstone formations, Carlsbad Caverns National Park, New Mexico

Ingo Arndt / Calcite flowstone formations, Carlsbad Caverns National Park, New Mexico

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....

John Cancalosi / Septarian nodule Calcite in clay, Sahara Desert, Morocco

Steven David Miller / Stalactities and stalagmites from calcite crystals, Tantanoola Cave, South Australia

JIM CLARE / Sparkling calcite floor stone in Mountain Cow Maga Cave, Belize, Central America

Bernard Castelein / Calcite springs overlooking Yellowstone River, Yellowstone NP, Wyoming, USA

Philippe Clement / Calcite springs and the Yellowstone river, Yellowstone NP, Wyoming, USA

Philippe Clement / Calcite springs and the Yellowstone river, Yellowstone National Park, USA

Gerry Ellis / Camelthorn (Alhagi maurorum) trees and calcite between dunes at Dead Veil, Namib-Naukluft National Park, Namibia

Paul D Stewart / Skull of extinct lemur (Mesopropithecus dolichobrachion) with calcite surface crystalisation, discovered by the photographer in the Ankarana Caves of Northern Madagascar. Pictured on site in 1987, the...

John Cancalosi / Fluorite with Calcite, (CaF2-calcium fluoride). Fluorite is one of the most popular minerals among collectors, Mineral class: Halides. Fluorite is a source of fluorine-used in the manufacture of milk...

John Cancalosi / Fluorite with Calcite, (CaF2-calcium fluoride). Fluorite is one of the most popular minerals among collectors, Mineral class: Halides. Fluorite is a source of fluorine-used in the manufacture of milk...

John Cancalosi / Chalcopyrite, Calcite, Siderite, Quartz and Dolomite. Sample from Hartenstein near Schneeberg Saxony in Germany.

John Cancalosi / Calcite (CaCO3), one of the most common and variable minerals on earth, used in building, metallugy, fertilizers, chemical industry, rhodochrosite, MnCO3, manganese carbonate, an ore of manganese when...

John Cancalosi / Chalcopyrite (CuFeS2, copper iron sulphide) (Golden variety), and galena on calcite. The major ore of copper, of high economic importance. Sample from Santa Eulalia, Mexico.

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 / Manganoan calcite (red), ferromanganoan dolomite(yellow). Sample from Krushev Dol mine, Madan, Bulgaria.

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 / Duftite (Lead-calcium / copper-zinc arsenate hydroxide) on Calcite, an oxidation product of weathered ore deposits. Tsumeb, Namibia

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 / Quartz on calcite. Baia Mare, Marmures county, Romania

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 / 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

Ingo Arndt / Calcite flowstone formations, Carlsbad Caverns National Park, New Mexico

Ingo Arndt / Camelthorn (Alhagi maurorum) trees and calcite at Dead Veil, Namib-Naukluft National Park, Namib Desert, Namibia