Strange Rocks Identification

[Thamil9897]

These strange specimens were found by my wife at a lake in Grant county West Virginia. I know nothing about geology so I thought perhaps you guys could give me a hand in identifying what type of rocks these are and how they were formed. 

Thank you in advance for any help!

[Steve Herschbach]

It appears to be voids or vugs in a fine grained layered sedimentary rock of some sort. I’ve seen similar, nothing to get particularly excited about, but unusual. If you have a university geology department nearby or a rock club they can probably give you more information.

http://downloads.wvgs.wvnet.edu/pubcat/docs/FTG-9_WVGES-ESAAPG17_FieldTrip_US48-CorridorH.pdf

[Joe D.]

To me it resembles the large iron chunks i sometimes find on the beach! Are they magnetic at all? 

[DDancer]

What you have are sedimentary concretions. They can come in some pretty neat formations.  Here's a link with some photo's and info on concretions : https://www.thoughtco.com/gallery-of-concretions-4122853

[Jeff McClendon]

Hi,

I am in agreement with DDancer. Those are definitely sedimentary concretions. Concretions form fairly early during the deposition of sedimentary rocks which are what you have a whole lot of in West Virginia. Spaces and cracks in the sedimentary formation are filled with a liquid mineral rich solution. The liquid evaporates and calcium, silicate and or iron oxide rich minerals fill the spaces. They are usually harder than the original sedimentary rock which later sometimes can weather away and leave the harder "concrete" walls. They can be fairly round, elongated or very irregular shaped but usually have holes, tubes etc. Concretions can also form around bacteria rich sediments and even around organic plant and animal remains which later disappear.

Jeff

[Joe D.]

Thanks Jeff and DD,

    I always learn new stuff on this forum!⛏👍

[Thamil9897]

Thank you so much for the quick informative replies, You guys rock!