While in Vermont for a construction weekend,we did use Sunday morning to start a mosaic collaboration. I envisioned a concave dish carved into the face of this rock while we were transcending fear shingling the main roof last year. Louise added the request for a spiral. I did the cutting with the diamond grinder, but we had to pack out before any contrasting material could be grouted into the channel. I would venture to guess it will still be there next week, when we return.