What is a concretion in geology ?

Concretion : definition

A concretion is a thickening by accretion of material around a nucleus or surface. The concretions are usually formed by successive deposits of chemical origin (precipitation of dissolved salts) or biochemical (intervention of living organisms which fix mineral substances).
 
The concretions are known in very many geological environments (caves, veins, stratiform deposits, karsts, etc...). The minerals deposit there in concentric layers giving a concretionated texture.

ReCaptcha

This service is used to secure web forms of our website and required if you want to contact us. By accepting it you agree to Google's privacy policy: https://policies.google.com/privacy

Facebook

Our website allows you to like or share its content on Facebook social network. By activating and using it you agree to Facebook's privacy policy: https://www.facebook.com/policy/cookies/

YouTube

Integrated videos provided by YouTube are used on our website. By accepting to watch them you agree to Google's privacy policy: https://policies.google.com/privacy

Twitter

Integrated tweets and share services of Twitter are used on our website. By accepting and using these you agree to Twitter's privacy policy: https://help.twitter.com/en/rules-and-policies/twitter-cookies

PInterest

Our website allows you to share its content on PInterest social network. By activating and using it you agree to PInterest's privacy policy: https://policy.pinterest.com/en/privacy-policy/