Doesn’t really look old to me. The writing is still white after more than 600 years? Not likely.
There’s a short but very good discussion at the Wikipedia link.
Wikipedia isn’t a Mormon site, and I’m not sure wth svcw was getting at with that nasty remark.
The stone can’t be dated by patination, because it’s been cleaned a number of times since 1880. The text must have been traced in white sometime after the 1960s, because the photo of the stone I remember from back then didn’t show this.