Editing Calcium silicate (section)

==Production and occurrence==
Calcium silicates are produced by treating [[calcium oxide]] and [[silicon dioxide|silica]] in various ratios.  Their formation is relevant to [[Portland cement]].<ref>H. F. W. Taylor, ''Cement Chemistry'', Academic Press, 1990, {{ISBN|0-12-683900-X}}, p. 33–34.</ref>

Calcium silicate is a byproduct of the [[Pidgeon process]], a major route to [[magnesium]] metal.  The process converts a mixture of magnesium and calcium oxides as represented by the following simplified equation:<ref>{{cite book |doi=10.1002/14356007.a15_559 |chapter=Magnesium |title=Ullmann's Encyclopedia of Industrial Chemistry |date=2003 |last1=Amundsen |first1=Ketil |last2=Aune |first2=Terje Kr. |last3=Bakke |first3=Per |last4=Eklund |first4=Hans R. |last5=Haagensen |first5=Johanna Ö. |last6=Nicolas |first6=Carlos |last7=Rosenkilde |first7=Christian |last8=Van Den Bremt |first8=Sia |last9=Wallevik |first9=Oddmund |isbn=978-3-527-30385-4 }}</ref>
:{{chem2|MgO*CaO +Si -> 2 Mg  + Ca2SiO4}}
The calcium oxide combines with silicon as the oxygen scavenger, yielding the very stable calcium silicate and releasing volatile (at high temperatures) magnesium metal.

Via the [[carbonate–silicate cycle]],  carbonate rocks convert into silicate rocks by [[metamorphism]] and [[volcanism]] and [[silicate]] rocks convert to [[Carbonate rock|carbonate]]s by [[weathering]] and [[sedimentation]].<ref>{{Cite journal |last1=Berner|first1=Robert |last2=Lasaga|first2=Antonio |last3=Garrels|first3=Robert |date=1983 |title=The carbonate-silicate geochemical cycle and its effect on atmospheric carbon dioxide over the past 100 million years |journal=American Journal of Science|volume=283|issue=7|pages=641–683 |bibcode=1983AmJS..283..641B |doi=10.2475/ajs.283.7.641|doi-access=free}}</ref><ref name=Walker1981>{{Cite journal|last1=Walker|first1=James C. G.|last2=Hays|first2=P. B.|last3=Kasting|first3=J. F. |date=1981 |title=A negative feedback mechanism for the long-term stabilization of Earth's surface temperature|journal=Journal of Geophysical Research: Oceans|language=en|volume=86|issue=C10|pages=9776–9782 |bibcode=1981JGR....86.9776W |doi=10.1029/JC086iC10p09776 |issn=2156-2202}}</ref>

The production of [[sulfuric acid]] from anhydrous calcium sulfate produces calcium silicates.<ref>[https://www.cementkilns.co.uk/cement_kiln_whitehaven.html Whitehaven Cement Plant]</ref> Upon being mixed with [[shale]] or [[marl]], and roasted at 1400&nbsp;°C, the sulfate liberates [[sulfur dioxide]] gas, a precursor to [[sulfuric acid]]. The resulting calcium silicate is used in [[cement]] [[Clinker (cement)|clinker]] production.<ref name="anhydrite process">[https://www.cementkilns.co.uk/cemkilndoc054.html Anhydrite Process]</ref>
:{{chem2|2 CaSO4 + 2 SiO2 + C → 2 CaSiO3 + 2 SO2 + CO2}}