Strange geological formation, what is it

[Rgk50]

 

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[NJearthman]

Pretty wild….a location town ,county and state could help narrow down an ID. Outcrop looks to be loaded with sphere-like concretions similar to moqui balls but not as smooth.
https://geology.utah.gov/map-pub/survey-notes/glad-you-asked/moqui-marbles/

 

[dognose]

it looks like to me a formation of geodes in the matrix where they form which the matrix also formed into stone.

An interesting formation for sure.

 

[Rgk50]

High Bruneau desert Idaho, appears a small percentage with the crystal like center, most with stone center, and, some seem to encase a smaller stone sphere

 

[Travelinman84]

digging. Looks to me like possibly a water or gas infusion in volcanic rock.

 

[Mackaydon]

Reminds me as a kid using a screwdriver and hammer to dislodge garnets from a large rock and collecting them in a Mason jar. Thanks for the memory reminder.
Don.....

 

[RTR]

Wow that is strange

 

[NJearthman]

This outcrop intrigues the hell out of me. I can’t believe there is nothing in the geologic literature of the area that mentions these red sandstone nodules in a black matrix.

 

[galenrog]

Geodes. The general area of Bruneau Canyon has at least 20 known geode sites.

Time for more coffee.

 

[NJearthman]

I asked the Idaho Geological Survey about this outcrop -here is their response:
It looks like you have some well-developed spherulites that formed in what is almost certainly a rhyolite. These form when the original glass recrystallizes as feldspar and quartz. When hollow, the term lithophysae is used, and that is how you get thunder eggs, the Spencer opal deposits, and geodes. Those with the crystals in the center are geodes. Hot fluids percolating through the rhyolite after the spherulites form carry the silica needed to form opal, agate, and quartz crystals.



These spherulites are probably from one of the many rhyolitic ash-flow tuffs in the region that formed in massive eruptions as a result of the passage of the Yellowstone hot spot. Rhyolite tuffs form when hot ash lands and welds back together. If that happens quickly enough, glass forms. It is that glass that will sometimes recrystallize.



An old USGS geologic map that shows the distribution of the various rhyolites is available here: https://ngmdb.usgs.gov/Prodesc/proddesc_9085.htm

 

[pspr]

Petrified alien excrement left many thousands of years ago.