It's all about the stone. I think one should collect jade for its beauty not its age. Two examples - one, a close-up of the corner of a Zhou dynasty cong; the other of eighteenth century cats - nearly three millennia apart but they give me the same pleasure.

W

PS. I meant to say, Chris, you're dead right about the carving; that's what's so wonderful about some of the best jades from the Zhou dynasty on (and even, less commonly, in the Shang); almost the whole surface had to be carved away in order to accentuate the design so that it looks and feels as though it's raised up rather than incised.