One of my favorites...

[Speedmaster]

Petrified ant village? Roots? What is it? I don't know but I had to drag it home. Its about a 8x8 slab of sandstone...

[cgode]

Petrified alien skin.....I knew they were here! hmy:
I....have......no......idea :S

[Speedmaster]

If I stare it this picture for too long it makes my brain twitch... :blink:

[CMD]

I have no idea, but I'm sure Roger will know

[tomclark]

septarian nodule??

[Bone2stone]

tomclark wrote:

septarian nodule??

  TAAA  DAAA!!!
Bone2stone

[Speedmaster]

Thanks! Dang you guys are good...

[painshill]

[QUOTE]Bone2stone wrote:

septarian nodule??

TAAA DAAA!!!
Bone2stone
Oooooh!…. Nearly, but not quite. Nice specimen. Ryan, assuming your description of it being a “slab” is accurate, what you have there is a planar, sedimentary version of a septarian nodule (more properly septarian concretion). We call this rock “septarium”…. also colloquially known as “turtle stone”.
As such, it’s a relatively rare rock formed from sediments in a bedding plane rather than the more usual discrete egg-shaped nodular lumps of it embedded in other rocks… frequently sandstone.


Septarian concretion



Septarium


The name derives from the Latin “septum” (plural: septa”) which means “partition”. In sandstone that has formed from material rich in clay or organic sediment, cracks arise from dehydration and shrinkage. Those cracks frequently fill with crystalline material precipitated from percolating groundwater which then lithifies. Calcite would be typical, but quartz is also possible.

Sometimes the cracks don’t fill with minerals and you then get this kind of effect:

http://www.flickr.com/photos/emilywatson/2560926269/

Septarian cracks are normally fairly angular but can be distorted by pressure before the mass has solidified.

Painshill

[Bone2stone]

[QUOTE]painshill wrote:

[quote=Bone2stone post=42565]

septarian nodule??

  TAAA  DAAA!!!
Bone2stone
  Oooooh!…. Nearly, but not quite. Nice specimen. Ryan, assuming your description of it being a “slab” is accurate, what you have there is a planar, sedimentary version of a septarian nodule (more properly septarian concretion). We call this rock “septarium”…. also colloquially known as “turtle stone”.
As such, it’s a relatively rare rock formed from sediments in a bedding plane rather than the more usual discrete egg-shaped nodular lumps of it embedded in other rocks… frequently sandstone.

Septarian concretion

Septarium
  The name derives from the Latin “septum” (plural: septa”) which means “partition”. In sandstone that has formed from material rich in clay or organic sediment, cracks arise from dehydration and shrinkage. Those cracks frequently fill with crystalline material precipitated from percolating groundwater which then lithifies. Calcite would be typical, but quartz is also possible.
Sometimes the cracks don’t fill with minerals and you then get this kind of effect:

http://www.flickr.com/photos/emilywatson/2560926269/

Septarian cracks are normally fairly angular but can be distorted by pressure before the mass has solidified.
Painshill
  Tomato/Tomahto
Yeah Rogers right.
I did not stop to think....
BTW: We got'em here in the Dallas area in the Eagleford as nodules and in the Woodbine as slabs.
Some in the Eagleford contain vast amounts of micro and macro fossils.
It's been a long time since I've heard of the nodules being referred to as "turtles".
Put it under a Black light it may be flouresent. Ours have a green and some have orange flouresence.
Some have none at all...
I'll try to find some of mine from both deposits.....
Bone2stone

[Speedmaster]

Wow! thanks for the info. Here's a pic of the whole thing. When I said 8x8 i meant inches.

[roustabout149]

Wouldn't want to be lost in that maze!  That's a really cool find.
Pam

[Marrattukka]

Wow that is pretty cool stuff. I think that when I was told there are alot of know it all's here it was the truth :laugh:

[rmartin]

Marrattukka wrote:

Wow that is pretty cool stuff. I think that when I was told there are alot of know it all's here it was the truth :laugh:

  There are some vey knowledgeable people here with many years of study and experience. "No it alls", I don't think so.

[Marrattukka]

Ray I didnt meen that in a diragatory way and hope I didnt offend you and if so sorry bro.

[painshill]

Marrattukka wrote:

Wow that is pretty cool stuff. I think that when I was told there are alot of know it all's here it was the truth :laugh:

  Todd, I completely understand. It can look that way can’t it? The other side of the coin is that folks often use websites like ours as reference sources and the stuff we post will also ultimately get picked up by search engines. We should take great pride in that and do our best to ensure that what’s on offer is accurate to the best of our knowledge. Otherwise, that’s how misinformation gets propagated, with a belief that it's authoritative.
Painshill