Chert? Algae Mats? Bif?

[fosceal2]

My brother in law calls this stuff chert , they use it like gravel when it is small. I have not been able to locate a source as when I see it it is in a creek or has slid down the mountain side to a road.

The whiter the background the more chalk like it feels, the greyer stuff is denser and more quartz like in feel. Out of the hundreds of lbs I have collected Only three had fossils ( clear shell imprints, one with an actual shell). The whiter ones grow lichens or algae like limestone.

I wonder is this Banded iron Formation rock like Dr.Bruce Stinchcomb describes in his Worlds oldest fossils book?

I have more pictures at photobucket under FOSCEAL album chert.

The graining looks woodlike but this is not wood. Any thoughts appreciated.

Cecelia

[jkfoam]

Cecelia,

If I had found that rock I would call it Chert or Flint. We find chert or flint nodules imbedded in limestone frequently here in central texas but none is as colorful as the piece you have. Ours are generally brown and tan, some with banding. The age of the piece would be equivalent to the host rock that contained the nodule.

JKFoam

[worthy 55]

Could it be petrified wood ?? Cool looking anyways!

[fosceal2]

Here is why I do not believe it is wood. I have found this shell and one other plus some snail? Limpit looking impressions.

It does have a grain look though and I do wonder is it caused by algae growth or is it just mineral.

Thank you to gentleman from TX. I am from Virginia Beach, VA. We had grey sand, grey clay, and grey concrete. I am still learning the basic rock names.

The colors of this Chert are just fascinating to me. Imbedded in Limestone? Hmmm like pockets of it? Same age as host rock. Cool OK now as soon as it warms up enough for me I am going to WV and see if I can find some -like a seam -in situ .So if I do and it is in fossil limestone that can be dated by common fossils then I will have backed into age of this rock- Correct?

Cecelia

[Gatorman]

wow thats some pretty stuff

[Guest solius symbiosus]

Google "mohs scale of hardness". If it is chert, it should be about 7.

The dark and light bands are probably the same material. If they weren't, one would see differential rates of weathering.

[tomclark]

Looks more like nice quality Agate than average chert although I believe geologically they are the same thing. agate chert, jasper,etc. Agatized shells or fossiliZed in that way are often found, in sedimentary layers within limerock and other types of sedimentary deposits, often with clay layers above and below them.

[Guest solius symbiosus]

Looks more like nice quality Agate than average chert although I believe geologically they are the same thing. agate chert, jasper,etc. Agatized shells or fossiliZed in that way are often found, in sedimentary layers within limerock and other types of sedimentary deposits, often with clay layers above and below them.

I use chert as a catch all term for all the variations of chalcedony.

[Ted]

That is beautiful chert , I would look for the layering to be sponge . The shell fossil would be unlikely to be with banded iron stromatolite .