Help With Info On Marine Fossils Found

[theoriginalrods]

Hi,

My name is Rodney and I am a fairly new fossil hunter from HUmboldt County, coastal Northern California.What prompted me to write this post is some shells that I found at the beach on the south jetty recently. They are all between 2-3". My wife found the whole shell (second picture) when she was walking our dog there. I'm guessing it's a fossil of a cockle shell in limestone or shale. I went to the same spot to check it out. The last two times I went I found these shell fragments which appear to be agatized. Could these be fragments of fossils which have been filled in with or attached to chalcedony or quartz? One of them has a bluish moonstone like iridescence and they all appear to have banding. Is this possible or am I mistaking shells for something else? They seem too thick to be shells. Any help would be greatly appreciated. I'm going to keep going back to look for more; these are cool and I've never found anything like them on the beach before.

Also if anyone knows of any good local spots or tips that would be great. I have checked out a few helpful websites, but I'm still not entirely sure what to look for.

Thanks,

Rodney

[Auspex]

The degree of mineral replacement is dependent on many variable factors. You can place a drop of vinegar in an inconspicuous place to see whether it bubbles at all; a reaction indicates the presence of calcium carbonate, which would suggest at least that the shells are not completely replaced.

[theoriginalrods]

ok thanks, I'll try that