Skeletons, fossils and calcium compounds. Calcium Calcium is a relatively reactive metal and so is...
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Transcript of Skeletons, fossils and calcium compounds. Calcium Calcium is a relatively reactive metal and so is...
![Page 1: Skeletons, fossils and calcium compounds. Calcium Calcium is a relatively reactive metal and so is normally found combined with other elements in compounds.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649f4f5503460f94c711c6/html5/thumbnails/1.jpg)
Skeletons, fossils and calcium compounds
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Calcium
Calcium is a relatively reactive metal and so is normally found combined with other elements in compounds.
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Bones and calcium
The adult skeleton contains around 1 kg of calcium, as calcium phosphate Ca3(PO4)2.
This explains why it is important to have a good source of calcium in the diet.
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Calcium and eggs
Calcium carbonate.It is the major component of eggshells.
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Many animals also have shells composed of calcium carbonate.
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Crystal form and structure.
Over most of a shell crystals of calcium carbonate are columnar.
If they form thin plates a very different material results, mother of pearl.
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Corals also have skeletons of calcium carbonate.
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Calcium carbonate and rocks.
Limestone is also largely composed of calcium carbonate.
Bath Stone (Greater Oolite) is a limestone that was laid down in the Jurassic period, c180 – 140 million years ago.
It is composed of many tiny ooliths, egg stones, formed by chemical precipitation from warm tropical seas coating small fragments of shell in layers of lime
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Many hot springs also precipitate a form of limestone, known as travertine, as their waters cool.
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Bioclastic limestones
Bioclastic (broken life) limestones are full of fossils.
Eg; Mountain Limestone from the Mendip Hills that formed in tropical waters c340 million years ago.
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Chalk
Chalk is almost pure calcium carbonate, made up of the microscopic shells of plankton.
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Marble
Under high temperature and pressure calcium carbonate in limestone recrystallises to form marble.
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Fossils
• Fossils are the remains of prehistoric plants and animals.
• Recent fossils are the actual remains of shells and bones.
• They have been almost unchanged by burial.
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Petrification
• Many older fossils have been petrified, turned to rock.
• Mineral rich waters percolating through the fossil having replaced its minerals with new compounds.
• In petrified wood preservation can be so perfect that the details of each cell can be made out.
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Casts and moulds.• In most fossils the original material has been entirely dissolved away, leaving a cavity in the rock.
• These cavities act as moulds, which are infilled by other minerals to form casts.