soapstone

soapstone (SOHP-stohn) - n., a soft metamorphic rock used for carving.


It's basically metamorphosed talc with a few other minerals (some mix of serpentine, magnetite, dolomite, and calcite). It's soft enough, it often has an almost soapy feel, thus the name. While it gets a patina, it doesn't weather much and its thermal properties make it also good for fireplace lining.


Thanks, WikiMedia!

---L.