What kind of clay is used to make old incense burners?

I've been trying to find this particular clay or putty. It's not polymer/sculpey/fimo. It's generally brown, seems fairly durable, and feels a lot like pottery clay, but I know it didn't go into a kiln because I've seen in wrapped around bamboo, beads and stones. If it helps, it's often used to make or decorate old (and some new) incense burners. It's driving me crazy!! If anyone knows what it's called/where I can find some, I'd really appreciate it; thanks!