Flint(?) Concretion

My geodes aren't as "purty" :mrgreen: as the ones in Kevins link, here's one I picked up in Kentucky on a bank of Grant Lake. I'm not sure but I think the crystals are calcite?
 

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Terri;187974 said:
So, the differences in cryptocrystalline quartz, chalcedony, chert and flint

Hi all. First post.

I was taught that chert, flint, jasper, ect are colloquial terms for the mineral chalcedony which is composed of micro-crystalline SiO₂. Too, geodes have chalcedony rinds or they are just nodules. I have seen geodes with several generations of xl formation that led to total filling of the cavity.

Things might have changed. It has been 25 years since mineralogy and I haven't really kept up.
 
Terri;188052 said:
:welcome: Solius! Having had a mineralogy course you have a better grasp than I do on this topic.

Thanks for the welcome. Back when I had mineralogy, we studied crystallography the first semester and optics the second. Sadly now, my alma mater has reduced the class to one semester! How they could fit all that into one semester??? It probably needed 4 semesters for a decent into...

And paleontology? Wow! Invert paleo was, pretty much required, but now it isn't even offered.:sad:
 

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