What’s the difference between a concretion and a nodule

[Fossil finder 100]

I have tried looking up the difference between a concretion and nodule and can’t seem to get a clear answer. I have seen both terms used on the forum but don’t know the difference and would like a clear answer so I can know what I’m talking about. Thanks ahead of time! 

[Randyw]

In mineralogy a nodule is a small rounded lump of one single mineral or a combination of minerals. These are generally harder than the rock or sediment in which they're found. A concretion is a collection of hardened compacted matter that forms as a result of mineral precipitation in spaces between the particles.

[siteseer]

2 hours ago, Randyw said:

In mineralogy a nodule is a small rounded lump of one single mineral or a combination of minerals. These are generally harder than the rock or sediment in which they're found. A concretion is a collection of hardened compacted matter that forms as a result of mineral precipitation in spaces between the particles.

 

That's basically what my copy of the "Dictionary of Geological Terms" (Anchor Books, revised edition, 1976) says.  It adds that concretions are also harder than the surrounding rock.

[DPS Ammonite]

Look to Mindat for good geological definitions. Probably better than Wikipedia since real geologists / mineralogists usually help with the definitions.

 

https://www.mindat.org/glossary/concretion

 

https://www.mindat.org/glossary/nodule