出典:Wiktionary
出典:『Wiktionary』 (2026/04/03 17:03 UTC 版)
concretion (countable and uncountable, plural concretions)
出典:Wikipedia
出典:『Wikipedia』 (2011/04/24 23:49 UTC 版)
A concretion is a volume of sedimentary rock in which a mineral cement fills the porosity (i.e. the spaces between the sediment grains). Concretions are often ovoid or spherical in shape, although irregular shapes also occur. The word 'concretion' is derived from the Latin con meaning 'together' and crescere meaning 'to grow'. Concretions form within layers of sedimentary 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.