Murfreesboro, ArkansasIt’s hot and humid and your clothes are plastered to your body with sweat. The park is busy for a Wednesday. Everywhere you look around the 36-acre plowed field there is someone bent over, shoveling the reddish brown dirt into five gallon buckets. There is a water park and a hiking trail and a restaurant. But you aren’t staggering with your own bucket toward a muddy trough filled with dark water to do things you can do anywhere. No, your here for the same reason as everyone else. You want a diamond. And make it a big one.Crater of…