Im new to rock identification

[Jeffparadise]

The Rock was found in Central Texas in the river bed
Any help identifying exactly what it might be would be appreciated.

 

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[Back-of-the-boat]

geode

 

[sutphin]

HELLUVA A ROCK FIND NEW MEMBER. AND WELCOME TO TNET

 

[TheCannonballGuy]

Back-of-the-boat is right, it is definitely one of the many versions of Geode. I collected Geodes when I was a geology student and "rock-hound" in college, almost 50 years ago. Still got a few of them. The central cavity in yours got almost completely filled with Quartz crystals.

 

[Plug N Play]

Rhyolite thunder egg would be my guess.

 

[P.ALLEN]

it's got banding like a tree that tells me it's been built (Layers built up is key here)up over time so I'm leaning sedimentary but eventually partially replaced by silica (quartz basically), but yes it is a geode. Host rock I'm unsure about, I'm leaning towards a really crappy jasper or Rhyolite as P N P suggested.

 

[TheCannonballGuy]

Rhyolite is an igneous (volcanic) mineral. The geology of central Texas is sedimentary, not igneous. So I'm sticking with the Geode ID. I agree with P.Allen, a Jasper variety.

 

[huntsman53]

Rhyolite is an igneous (volcanic) mineral. The geology of central Texas is sedimentary, not igneous. So I'm sticking with the Geode ID. I agree with P.Allen, a Jasper variety.

I agree! The outer shell of the Geode appears to be a mix between Jasper and Chert or just different colored Jasper.


Frank

 

[Geochem]

Cannonball and Huntsman has pegged its identity. A nice banded microcrystalline quartz geode that shows past-period physical breakup and resolidification by quartz. The variations in the band coloring appear to be dominately elemental iron, iron hydroxide, and elemental manganese impurities during quartz-precipitation. Nice find!