Editing Concretion (section)

{{Short description|In geology, a type of compact mass}}
{{other uses|Calculus (medicine)|Enterolith|Nodule (geology)}}
{{Use American English|date=August 2021}}
[[File:Конкреции в Западном Казахстане. Concretions. Western Kazakhstan.JPG|thumb|Concretions in [[Torysh]], Western [[Kazakhstan]]]]
[[File:Konkrece Geologická zahrada DP Praha 2017 2.jpg|thumb|Concretions with lens shape from island in Vltava river, Prague, Czech Republic]]
[[File:Marlstone aggregate concretion (Sault Ste. Marie, Michigan, USA.JPG|thumb|[[Marlstone]] aggregate concretion, [[Sault Ste. Marie, Michigan]], United States]]
A '''concretion''' is a hard and compact mass formed by the precipitation of [[mineral]] cement within the spaces between particles, and is found in [[sedimentary rock]] or [[soil]].<ref>{{cite book|title=Glossary of terms in soil science|date=1976|publisher=Agriculture Canada|location=Ottawa|isbn=0662015339|page=13|url=http://sis.agr.gc.ca/cansis/publications/manuals/1976-glossary/pub1459_report.pdf}}</ref> Concretions are often ovoid or spherical in shape, although irregular shapes also occur. The word ''concretion'' is borrowed from [[Latin]] {{lang|la|concretio}} {{gloss|(act of) compacting, condensing, congealing, uniting}}, itself derived from ''concrescere'' {{gloss|to thicken, condense, congeal}}, from ''con-'' {{gloss|together}} and ''crescere'' {{gloss|to grow}}.<ref>{{OEtymD|concretion}}</ref> 

Concretions form within layers of sedimentary [[Stratum|strata]] that have already been deposited. They usually form early in the burial history of the sediment, before the rest of the sediment is hardened into rock. This concretionary cement often makes the concretion harder and more resistant to [[weathering]] than the host [[stratum]].

There is an important distinction to draw between concretions and [[Nodule (geology)|nodule]]s. Concretions are formed from mineral precipitation around some kind of nucleus while a nodule is a replacement body.

Descriptions dating from the 18th century attest to the fact that concretions have long been regarded as geological curiosities. Because of the variety of unusual shapes, sizes and compositions, concretions have been interpreted to be [[dinosaur]] eggs, animal and plant [[fossil]]s (called [[pseudofossil]]s), extraterrestrial debris or human [[Artifact (archaeology)|artifact]]s.