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Coral is a vast commune made up of tiny marine organisms called polyps, which are related to sea anemones.
Corals are of two types: perforate and imperforate. Perforate corals have porous skeletons with connections between the polyps through the skeleton. Imperforate corals have solid skeletons. Many corals have different growth forms. They can be plocoid as in Tubastrea coccinea (orange cup coral) and Favia fragum (golf ball coral). They can also be meandroid in which corallites form a series within the same walls, as in the species Dendrogyra cylindrus (pillar coral). Other growth forms include cocoid, spherical shaped and phalecoid, as in Eusmilia fastigiata.
Corals can obtain food in a variety of ways. Reef-building corals rely on the photosynthetic products of zooxanthellae for the majority of their nutrients. However, corals also capture zooplankton for food using their tentacles.
Coral is essential to the world's eco-system as it absorbs vast quantities of carbon dioxide from the water and converts it into calcium carbonate. More carbon dioxide is absorbed by the world's coral reefs than by the rain- forests on land. In 1998 70% of the world's coral was destroyed by a freak weather system, leading to fears that global warming could increase.
 Research Coral
Calcium is a lustrous silver-white brittle alkaline metal element with the symbol Ca. Its oxide occurs widely in nature as lime. It is a member of the alkaline earth group of elements.
Calcium occurs widely in nature, as in its compounds calcium carbonate or limestone,
calcium sulphate or gypsum, calcium fluoride (fluorspar), and calcium phosphate (apatite).
Research Calcium
Calcium carbonate is a natural occurring salt that is found in limestone, chalk, and marble. It is used as a pigment and for pigment prolonging.
Research Calcium Carbonate
A carbonate is a salt formed by the union of carbon dioxide with a base element, such as calcium carbonate; sodium carbonate; barium carbonate; sodium bi-carbonate. Many of the carbonates are extensively used in the arts and in medicine.
Research Carbonate
Raw sienna is a yellow-brown earth colour consisting chiefly of iron oxide and containing smaller amounts of silica, alumina, manganese oxide and calcium carbonate. Raw sienna is found mainly in Italy and Sicily, and gets its name from the Italian town of Sienna. Raw sienna is a somehat transparent, golden yellow pigment.
Research Raw Sienna
Stannic acid is a compound of tin. It exists in two forms, both solid distinguished as stannic and metastannic acids or as alpha- and beta-stannic acids. Stannic acid may be prepared by adding calcium carbonate to a solution of stannic chloride. It forms a series of salts known as stannates. Meta-stannic acid is obtained by the action of nitric acid on tin.
Research Stannic Acid
Calcareous refers to containing calcium carbonate or calcite.
Research Calcareous
Chalk is a pure soft limestone, opaque white, and usually formed by the accumulation of the shells of foraminifera together with those of larger marine organisms. Chalk is found in large quantities in land masses which were at one time covered by the sea. Chalk is composed of between 50 and 98 percent calcium carbonate and various of minerals including clay, hematite, mica, quartz and pyrite. Chalk is important in industry and is used in the manufacture of rubber goods, paint, putty, polishing powders, cement, as well as the familiar writing implements beloved by school teachers.
Research Chalk
Limestone is a sedimentary rock composed of calcium carbonate. It is used as a source of cement in the building industry and for blackboard chalk.
Research Limestone
Sandstone is a common sedimentary rock made up of tiny grains of quartz held together by a type of cement. Sandstone is produced by sand which has been deposited and cement precipitated between the grains by groundwater percolating through it. The most common cements are calcium carbonate, silica and iron oxide. Sandstone is an important building material in the USA where many of the brownstone houses in the north-east cities are made of sandstone.
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The Probert Encyclopaedia was designed, edited and programed by
Matt and Leela Probert
©1993 - 2009 The Probert Encyclopaedia
Southampton, United Kingdom
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