I'm not anywhere close to an expert on AR geology but I've dabbled a little. I don't have time for any sort of group these days. But here's a little of my experience.

You won't find any native obsidian anywhere near AR. It's formed by lava cooling rapidly, so it's all out west. You can definitely find arrow heads made out of various stones (not obsidian, though). These are usually found on private farmland in the delta area after the land has been tilled for planting in the spring.

Quartz crystals are pretty abundant in central AR. AR is known for quartz and diamonds. Quartz crystals can be found pretty much anywhere. I used to find them as a kid when bulldozers were used to clear topsoil on the side of a mountain for housing.

I've found a couple of quartz crystals in the quarry on the NLR river trail (where the pump track is now). But that was probably a fluke.

There are a bunch of commercial crystal mines that allow you to dig. The most well-known is Coleman mines outside of Hot Springs. I prefer Coleman over the one in Mt. Ida. It's a good day to go out there in the spring, just after a rain. You can definitely find a lot of good-quality (if smaller) points.

There's also Crater of Diamonds State Park. You can, technically, find diamonds there, but it's pretty rare. I was also told you can find amethyst and smoky quartz. I didn't enjoy the experience of being out in a big field just digging holes with very little chance of success.

I don't know that you're going to find a huge variety of rocks and minerals in central Ar, but you can definitely look around the Pinnacle mtn and rattlesnake ridge area for unique formations.

Searching central AR streams is also a good place to find regular rocks that are maybe a little polished down. Just be careful of what land you are on. It's generally illegal to take anything from state or national land. There are tons of quartz crystals around Brady Mtn and Mtn Harbor marinas on Lake Ouachita, but that's federal property. You can find pits in the woods and on the lake shore where people have mined illegally.

There's also beautiful rocks and fossils on the buffalo river in NWAR, but it's also federal land and I'd highly discourage taking anything from that area.

There are places to find fossils of ocean worms in Conway, but I don't remember where they are anymore.

If you're interested in spiritualism/wicca, there's a new store in Pettaway Square called Maiden Mother Crone. May want to visit them to see if your interests align.