please tell me what this is

[martyb]

I found this in the San Diego area, it is heavy, 6 lbs. size is 7" x 5" x 7". I was told it is around 5 million years old. can any one please give me some information on age. is it rarity, collectability, exactly what it is?

Thank You so much for your time

Martin 

[Kane]

This looks like serpulid worm tubes. I’m not sure of age. As for collecting, just about anything can be collected pending one's preference.  

[Fossildude19]

Probably Mid to Late Pliocene in age. I agree, they look like worm tubes, or some sort of infilled burrows. 

Probably not anything rare. Anything is collectable. 

We do not do provide monetary evaluations, per our rules. 

That said, don't write any big checks off of it.  

[DPS Ammonite]

Also consider calcareous coralline algae a possibility. The structures look rather thick to be the shell of a serpulid worm tube. I wonder if the holes are from something like a sea grass that an algae grew on.

[TqB]

Another possibility is a calcareous tufa, grown around plant material that has subsequently dissolved to leave the central hollows.

[DPS Ammonite]

Where were these found? What formation or age? What fossils were found near this?

 

Use this reference to find age of rocks and help you ID mollusks. 

http://olivirv.myspecies.info/sites/olivirv.myspecies.info/files/Fossil mollusks of San Diego County - Moore%2C Ellen James.pdf

 

Edited March 24, 2021 by DPS Ammonite

[Myrmica]

Here are some Serpulid worm tubes for comparison.  At first glance, your specimen does look like this but, on closer inspection, the walls of the tubes are much thicker and lack the surface texture, and the internal spaces, where the worms would have lived, are very small in diameter.    Happy collecting.