First steps into Floyd county Cambrian: Lots of nodules, not a lot of Trilos.

[MeargleSchmeargl]

I just went to the Floyd county Conasauga at a roadside site mentioned in https://www.researchgate.net/publication/264495630_Taxonomy_and_biostratigraphic_significance_of_some_Middle_Cambrian_Trilobites_from_the_Conasauga_Formation_in_western_Georgia (partly guided by a few locals). After searching, we found tons of nodules, and only a few exposed Trilo parts. It was only near the end of the trip that I realized that at this site, I might need to split the nodules open to find much in them. So I took a few decent sized ones with me to figure out what to do with them after I attempted to split a few, and only getting one open relaitively cleanly (nothing inside).

 

My immediate assumption is perhaps to use the freeze/thaw method I've heard people use for mazon creek nodules (instructions?).

 

Any other tips for splitting these nodules? They're much tougher that I personally thought they'd be (at least it was harder to actively split them on site, given their round shape makes it hard to keep the chisel going in one spot).

 

 

 

The site: 

 

 

Some of the numerous nodules present:

[FossilDAWG]

I have been to that site and had the same experience of a low yield of trilobites or trilobite parts.  Those nodules are highly silicified and they do not split, they shatter.  Also they break through, not around, any contained fossils.  In my experience, what you see on the surface is what you get.  Even if a fossil is evident but partly buried in the nodules, the silica is so hard you can't prep out the buried parts.

 

Don

[Auspex]

Zen fossils. They have become one with the rock.

[Plax]

You might try squeezing them slowly in a large vice. Where eye protection of course. The slow squeeze may cause them to break along weak planes better than the puntuated shock of a hammer.

[Mark Kmiecik]

On 4/13/2019 at 4:36 PM, MeargleSchmeargl said:

My immediate assumption is perhaps to use the freeze/thaw method I've heard people use for mazon creek nodules (instructions?).

The reason the freeze/thaw method works on Mazon Creek concretions is that they formed of iron siderite, a fairly porous material. The reason they split along the weakest plane is that there is enough of a gap that when soaked for a period of time, usually a week to ten days, that gap becomes filled with water that expands when frozen and causes the concretion to crack, eventually, in that plane. Depending on the porosity of the matrix, it may require up to a month of soaking and as much as 100 freeze/thaw cycles to get the job done. Even then it is not an exact process. If the material is not porous it won't soak up any water and the freeze/thaw method is useless. The concretion will crack from the outside in instead of inside out, resulting in many fragments. I've put some MC specimens back together from as many as 109 pieces, if they were very well preserved or just impressive enough.