Water As Shielding

> I don't want to build it out of sapphire for the sake of glitz or
> bling, I want to build it out of sapphire because of sapphire's
> wonderful properties and because of the fact that aluminum and oxygen
> are fairly common. For instance, it has been suggested to build a
> Stanford Torus out of one million tons of aluminum derived from lunar
> regolith. Well, the regolith contains more oxygen than it does
> aluminum, so if you could use both, you wouldn't have to mine as much,
> which would save money. And that's even assuming you wanted to use a
> million tons. If sapphire is so strong, tough, etc., you might want
> to use 750,000 Kg or even 500,000 Kg.