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[lithicbeads]

37 x 20 mm, 4 mm hole.  This is an aggregation of radiolarian fossils.  California

[vitzitziltecpatl]

Hmmm - always liked Guadalupe. Never knew those were little fossils.

Thanks!

[R.U. Sirius]

Hmmm - always liked Guadalupe. Never knew those were little fossils.

Thanks!

I think the fossils in this material (Radiolaria) would only be visible under electron microscope. Orbicular features are due to some staining and/or recrystallization process.

[lithicbeads]

There has been recent research stating that some are aggregations of fossils but some plainly visible ones are distinct individual animals with two core layers and a this layer of legs etc. Radiolarians are small now but these are quite old.

[irockhound]

Wow news to me,  Does that make Morgan Hill Poppy Jasper the Amazonian Version of the Radiolarians?

[lithicbeads]

I will look for his book but is I remember correctly he prefers the small dot poppy jasper as it can show external features at 30 X in cases so I imagine the big dots are all aggregations.

[R.U. Sirius]

By aggregations, you mean colonies (I found a few manuscripts mentioning how some radiolaria species would form colonies up to several cm in size; and some of those had silica skeletons)? These structures would need to survive post-mortem sedimentation, etching/redeposition of silica, and any diagenesis before resurfacing for us to find them as orbs. I am very curious to see any literature showing evidence of orbs in poppy jaspers being essentially fossilized colonies of protozoans.

Or did you mean aggregations of more conventional, individual silica skeletons during sedimentation/diagenesis?

I am still inclined to consider orbicular features in Franciscan materials a result of a strictly physical/chemical process of crystallization of the originally amorphous siliceous ooze, much like what we see in some rhyolites.