And the plot thickens. Obsessing over tiny geodes I found near lake/mchenry county il. I'm pretty sure they're Quartz. Found 2 more today, just on surface.
After more web searching, I was reminded about a small earthquake, January 31, 2012. 2.4 mag. Epicenter approx 1 mile from my home. Other sources say little is known about fault lines in n/e il and s/e wis.
I am so curious but completely without resources. I've reached out to the nearest mineral society that seems most legit, but they're 3 hours away near Iowa and so small there is no forum/chat or solid resources.
I'm reaching out to the experts... You guys!!!!

Thoughts? Opinions? Suggestions on how I can find out more?? I have another post about these tiny geodes on surface of cornfield I wrote yesterday with pics included.
Interestingly enough, found another post from someone in Illinois who did was sifting and panning somewhere in my area and found some stones he couldn't identify. I read that chain and made a guess... Spinel/spinel? Drift diamond?

My area is so strange and unresearched. Limestone quarries, lakes, smallish rivers, hills, (these hills start near my home and continue a bit west, but just east it becomes very flat heading back towards Lake Michigan) clay, farms (with fields of divers stones and minerals). We experienced several glaciers.. Thus some sporadic mineral deposits from glaciers. I've read there is a glacial "out wash" nearby in mchenry county. But again, history of earthquakes with really no info.

Ok, I'll stop but I'm obviously obsessed. The lack of info and even documented lack of true knowledge of the local topography due to soil/heavy glacial dirt/debris if you will... Along with knowledge there must be a fault nearby (again very little info and seemingly no follow up). Glaciers, earthquake faults, and tiny geodes... Where to go from here...

I got nothin'

I feel bad for having nothing, so poked around. McHenry County Geology

I like gold, so of course had to check this out: Illinois State Geologic Survey

Also found this map from USGS of the mineral industry in Illinois: USGS Illinois Minerals


You're right....Colorado is much better for geology :)

Great answer Emac, I was also going to suggest some USGS resources for this. Good info!

Thank you CP and EMac! I appreciate all of the info!!! Just read the link specific to McHenryCounty, probably going to go explore some glacial out washes. Still no answer on the tiny geodes, couldn't see any reaction but crystals so small/material so little, I cannot see clearly. Hoping to find a larger specimen to test.

I'll update my findings... When I have them, lol.

Best regards and happy hunting!!
GG

Mystery solved!!! Limestone!! Lots of it broken up by years of crops and and erosion and who knows what else. I've found slabs with little embedded geodes! I wonder what's deeper where the stone is probably larger and more dense!!! I'll post pics soon

I'm gonna go out on a limb and say....limestone?

Finding one of these in the limestone would make it pretty sweet!: New Type of Meteorite Discovered

I'm not an expert by any stretch of the imagination, but do you by chance have fracking in the area? I'm remembering reading something about Oklahoma having more quakes since fracking started. Just a thought.

Limestone is good stuff.

Geodes can form in limestone from any cavity that fills with silica. No volcanism needed.
What do you suspect is in the glacial outwash? I'm just curious.

Back home (Topeka,Ks) they have had earthquakes bad enough to shake their houses. Id never known of any quakes there before. Not good.