The Louisiana State Mineral is Agate and the State Fossil is Palm wood. Palm wood like most other petrified wood is indeed agate. Collecting in the Bayou State is a bit of luck but you might find some petrified palm wood in the Toledo Bend region along the border with Texas.
Though never designated as the state gemstone Louisiana Opal is a form of sandstone in which grains of sand are held together by clear opal.
Louisiana Opal has never been plentiful. Most of the mining went on in the late 1980s and early 1990s and most of that production was by a single individual who had a tightly held claim. Since his death Louisiana Opal is hard to find. You usually can purchase a sandstone opal from one of his proteges at the New Orleans Gem and Mineral show in October.
If your luck is not good for opals or petrified wood I promise you that you will eat some good food and pass a good time.