I started out using only Lyons sandstone in my table tops.  Susan Judy @Stonequiltdesign  or https://stonequiltdesign.com/  who is a master at incorporating a variety of semi-precious stones, suggested I explore incorporating focus stones in my designs.  Judy and I go to a lot of gem and mineral shows.  About 10 years ago a dealer from the Bad Homborg limestone quarries began showing slabs of limestone with dendritic intrusions.  These interersting paterns are not fossils, but they sure look like them.  Several large slabs caught my eye and a I paid way more than I expected.   

I particularly like this large ( about 10" wide ) stone with multiple patterns and made it into the table you see here.  I sold it to a colleage of mine.

Over the years the dealer has upgraded the stones he shows to include specactular fossils and raised his prices quite a bit.   

I have an inventory of stones like the one shown here and would be happy to include one of them in a table top for you.  If you ask I'll send you pictures of the available stones.

Bill