It looks like it might be azurite. Although not reported from Florida, there are deposits in the vicinity of New Orleans, towards Baton Rouge. It's a carbonate mineral so you might try wiping a small area with a cotton handkerchief dampened with a little lemon juice or vinegar to see if you get any colour transfer.
Cobalt blue glass. Either melted in fire or from old furnace or part of a glass cullet delivery that never made it to shore. Atleast that's my opinion,