Strange rock or fossil - Can anyone ID?

[Sweeby]

We found a very unusual rock or fossil in a load of bull rocks and I'm wondering if any of you can offer any insight. There are lots of limestone deposits, caves and fossils in our area, but this specimen was in a load of bull rocks used for landscaping, so probably from somewhere in central Texas.

 

It's about 15 CM long by 5 cm wide by 2 cm thick and is oddly structured. There are various layers that look biological in origin to me. The surface I'll call the 'top' resembled onyx in color and translucence with a 'bubbled' surface similar to a piece of bacon. In some areas, this layer appears to have been worn through. This layer looks like what I'd imagine 'fossilized fat' to look like.

 

Then come several layers of various colors (buff, tan, reddish) and thicknesses (2 - 4 mm) that appear to have a cellular structure, with tiny walls and pockets. These remind me of gills on a crab or lobster or perhaps petrified wood.

 

The surface I call the bottom resembles our area's limestone but is rough and pock-marked.

 

Any ideas?

 

[FranzBernhard]

12 minutes ago, Sweeby said:

limestone deposits, caves and fossils

 

Welcome to TFF from Austria!

 

You are having a piece of flowstone, a typical cave formation.  It seems to have been dissolved somewhat after formation. After that, carbonate precipitation started again, possibly in a creek, forming the white crust.

 

Flowstone (link to wikipedia)

 

Franz Bernhard

[Ludwigia]

I agree. Crystallized calcareous sinter is another definition.

[Sweeby]

Thank you!  This makes a lot of sense given the area's geology.  I appreciate your insight!