Calcium is a lustrous silver-white brittle alkaline metal element with the symbolCa. 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
Apatite is a widely distributed accessory constituent in all classes of rock. Found in crystals and masses, crystallised apatite has been extensively used for fertiliser. Transparent varieties of a fine colour are sometimes used for gems - but it's too soft for extensive use. Apatite has the formulae Ca5(F,Cl,OH)(PO4)3 and a relative hardness of and crystallizes in a regular six-sided prism, usually terminated by a truncated six-sided pyramid. It passes through various shades of colour, from white to yellow, green, blue, and occasionally red, scratches fluorspar but is scratched by felspar, and has a specific gravity of about 3.5. It is a compound of phosphate of lime with fluoride and chloride of calcium. Research Apatite
Hardness refers to the resistance of a smooth surface of a rock or mineral to scratching. It is determined by the binding force of atoms within the crystal structure and is measured according to Moh's ten division scale of hardness, ranging from 1 the softest, to 10 the hardest: 1) talc 2) gypsum 3) calcite 4) fluorite 5) apatite 6) orthoclase 7) quartz 8) topaz 9) corundum 10) diamond.
Materials, according to this arrangement, which are scratched by quartz and are not scratched by felspar are said to have a hardness between 6 and 7.
Mimetite is an arsenochloride of lead and a minor ore of lead and has the formulae Pb5(AsO4)3Cl and a relative hardness of 4. It is a relatively rare mineral which occurs in the oxidized portions of lead bearing veins. Mimetite occurs in yellow, orange, brown, green and white colours and is related to and resembles pyromorphite. Milarite was identified in 1832 and belongs to the apatite group. Research Mimetite
Phenakite has the formulae Be2SiO4 and a relative hardness of 8. It is a rare mineral found in pegmatite dikes associated with topaz, beryl, and apatite. From the Greek word for 'a deceiver' in that it can be mistaken for quartz. Research Phenakite
Phosphorite is an impure massive form of apatite, mined for the calcium phosphate it contains, and forming one of the chief sources of phosphorus and its compounds, and of artificial manures. Research Phosphorite
Abbreviations
Research Calcium
