This unidentified fossil could possibly be a leg bone fragment of a massive animal, considering how flat one side is, then the short face takes a perfect 90 degree angle.
It popped out of the deep clay off Venice Beach Florida where Pleistocene fossils are common. Rather than being exposed to lots of additional wear from surf exposure, it was dug freshly, so loads of extremely fine detail is intact.
Length: Just under 8 1/4 inches (just under 21 cm)
Weighs: 283 grams
This fossil is quite strong (not particularly brittle) but it is porous, not agatized, solid quartz, or suitable for polishing or making cabochons. Great as-is.