It can be soft or hard. So when I work with sandstone I'm constantly sharpening tools, even though I use Tungsten chisels which are very hard, very tough. The very hard sandstones you can get as good a detail in a piece of carving, as fine a detail as you can in any other stone that I know of. Any other stones of course are marbles. But it's still kind of expensive.
Marble is a crystalline sort of stone.
And so that gives it a property whereby when you work the stone and then polish it light actually can go down into these crystals which are relatively clear, especially in white marble, and go down into the stone a depth and then be reflected back up. So when you look at a piece of marble it has this lustre and this depth. And of course the great thing that people have always used it for is that it mimics to some extent the quality of human skin, in that our skin is translucent, and so when you look at somebody you're actually looking at the light coming back through from a depth within them, and that gives their face a glow. And to some extent marble can mimic that.