redesign of ONeill cylinder mirrors

--- In spacesettlers, "millenial70" wrote:

> It could make for a more sound structure as the cylinder would be
> composed of one strong material, and not half of it as glass (or
> is it quartz or something else?).

Why not sapphire? Aluminum and oxygen, and if VVD'ed, should be easy
enough to deposit as sapphire.