Nautaloid?

[Apophis]

Howdy folks,

 

Last weekend I returned to a place in Texas that I have collected marine fossils at previously. The owners of this area have specifically asked that I not share any details on the location, but it’s a bit of an anomaly as it appears to have a number of fossil bearing matrix including sandstone, shale, limestone, and the thickest mud I’ve ever seen. It doesn’t match any of the USGS data either.

 

I found a number of things there that I would like to preset, but the main one is this:

 

The little plates that make up this stone form a spiral and they shine like opal / ammolite. This tear drop shape is something I’m familiar with as I have another one, smaller, that also shines, as well as chert nodules of the exact same shape that I suspect are related. 
 

Here are a few other things I collected at this location:

 

 

 

 

 

this piece of limestone is rather large, about 20lbs, and it’s filled with things I’m not even remotely qualified to ID. It deserves its own post which at some point I’ll get around to. 
 

 

I collected this at the same location years ago. I think it’s an orthocone or pseudo-orthocone nautaloid. Well, half of one at least. Not sure really, but it also deserves its own post. 

[Kane]

First two items are just chert or agate.

The second last photo does appear to have marine fossils. I think I can detect some shell material. 

[Fossildude19]

Your first two look like quartz or agate, to me.

Your third and fourth items are something, but the others don't appear to be fossils, to me.  

The last one shows no camerae of an orthocone cephalopod. I see no siphuncle, or even orthocone shape to this item.   

 

 

[Apophis]

On 9/12/2020 at 2:11 AM, Kane said:

First two items are just chert or agate.

The second last photo does appear to have marine fossils. I think I can detect some shell material. 

There does appear to be what looks like aragonite running through it. Unfortunately there isn’t a lot visible. It was only presented in an attempt to provide some context and show why I leaned toward marine fossil. Regarding the others items, when you say “Just chert or agate”, is that regarding opal, fossil, or both? 
 

On 9/12/2020 at 7:45 AM, Fossildude19 said:

Your first two look like quartz or agate, to me.

Your third and fourth items are something, but the others don't appear to be fossils, to me.  

The last one shows no camerae of an orthocone cephalopod. I see no siphuncle, or even orthocone shape to this item.   

 

 

Thank you for the photo! This is exactly what I need. 

[Kane]

Agate has a micro- or cryptocrystalline structure that opals do not. I would not say they are equivalent. Chert is also quartz-based, but is generally the result of biogenic, siliceous ooze. In some formations, a high abundance of chert is indicative of the presence of sponges. In this particular instance, I would say the first two pieces more resemble agate as opposed to chert.