Help with an ID of this rock...

[GodOfRustyNails]

A buddy of mine found this in Bloomington... any idea what it is or what causes the odd formations within
Thank you,
Steve

 

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[centfladigger]

it looks like a type of druzy like we have in our coral down here. I have some of what your holding but cant remember the name, mine is solid and a nice yellow with pink, I`ll find out if someone else doesnt chime in

 

[Goodyguy]

A buddy of mine found this in Bloomington... any idea what it is or what causes the odd formations within
Thank you,
Steve

That is a geode and the formations are caused by mineral sedimentation.

It goes like this: The geode cavity formed in a roundabout way, from a hard little nodule that later dissolved away, leaving a void. The process started about 350 million years ago when limey sediments built up in warm, shallow seas that covered what is now central United States. The salty warm waters seeped through calcite-rich limey sediment; the salt reacted with the calcite (which is an ingredient in limestone, chalk and marble), and transformed the calcite into the minerals.

Those type geodes are common to central Indiana.

GG~

 

[GodOfRustyNails]

That is a geode and the formations are caused by mineral sedimentation.

It goes like this: The geode cavity formed in a roundabout way, from a hard little nodule that later dissolved away, leaving a void. The process started about 350 million years ago when limey sediments built up in warm, shallow seas that covered what is now central United States. The salty warm waters seeped through calcite-rich limey sediment; the salt reacted with the calcite (which is an ingredient in limestone, chalk and marble), and transformed the calcite into the minerals.

Those type geodes are common to central Indiana.

GG~

Cool! This solves the mystery and a little lesson as well.
Thank you,
Steve