Editing Calcite (section)

== In Earth history ==
[[Calcite sea]]s existed in Earth's history when the primary inorganic [[Precipitation (chemistry)|precipitate]] of [[calcium carbonate]] in marine waters was low-magnesium calcite (lmc), as opposed to the [[aragonite]] and high-magnesium calcite (hmc) precipitated today.  Calcite seas alternated with [[aragonite sea]]s over the [[Phanerozoic]], being most prominent in the [[Ordovician]] and [[Jurassic]] periods.  Lineages evolved to use whichever [[Polymorphism (materials science)|morph]] of calcium carbonate was favourable in the ocean at the time they became mineralised, and retained this mineralogy for the remainder of their evolutionary history.<ref name='Porter2007'>{{cite journal |doi=10.1126/science.1137284 |title=Seawater Chemistry and Early Carbonate Biomineralization |year=2007 |last1=Porter |first1=S. M. |journal=Science |volume=316 |page=1302 |pmid=17540895 |issue=5829 |bibcode=2007Sci...316.1302P |s2cid=27418253}}</ref> [[Petrography|Petrographic]] evidence for these calcite sea conditions consists of calcitic [[ooid]]s, lmc cements, [[hardgrounds]], and rapid early seafloor aragonite dissolution.<ref>{{cite journal |doi=10.1080/00241160410002135 |title=Calcite precipitation and dissolution of biogenic aragonite in shallow Ordovician calcite seas |year=2004 |last1=Palmer |first1=Timothy |last2=Wilson |first2=Mark |journal=Lethaia |volume=37 |issue=4 |pages=417–427 |bibcode=2004Letha..37..417P}}</ref> The evolution of marine organisms with calcium carbonate shells may have been affected by the calcite and aragonite sea cycle.<ref>{{cite journal |author1-link=Elizabeth Harper (biologist) |author=Harper, E.M. |author2=Palmer, T.J. |author3=Alphey, J.R. |year=1997  |title=Evolutionary response by bivalves to changing Phanerozoic sea-water chemistry |journal=Geological Magazine |volume=134 |issue=3 |pages=403–407 |doi=10.1017/S0016756897007061 |bibcode=1997GeoM..134..403H |s2cid=140646397}}</ref>

Calcite is one of the minerals that has been shown to [[catalysis|catalyze]] an important biological reaction, the [[formose reaction]], and may have had a role in the origin of life.<ref name=Hazen/> Interaction of its [[Chirality|chiral]] surfaces (see [[#Form|Form]]) with [[aspartic acid]] molecules results in a slight bias in chirality; this is one possible mechanism for the origin of [[homochirality]] in living cells.<ref>{{cite book |last1=Meierhenrich |first1=Uwe|title=Amino acids and the asymmetry of life caught in the act of formation |date=2008 |publisher=Springer |location=Berlin |isbn=9783540768869 |pages=76–78}}</ref>