Re: are x-rays reflected by mirrors (aluminum), absorbed or do they penetrate.

X-rays are not reflected by aluminum mirrors in the same way that light
rays are.  A typical X-ray will penetrate through thin layers of aluminum,
and eventually be absorbed by the material.  I'm not sure exactly how thick
the layer must be to absorb the X-ray.

If an X-ray strikes a metal surface a very glancing blow, moving almost
parallel to its surface, then it may be reflected at an equally glancing
angle.  Astronomers have used this glancing-incidence reflection to build
telescopes which can focus X-rays; they are MUCH more difficult to build
than mirrors for ordinary light.  You can see an example of an X-ray
telescope by going to http://chandra.harvard.edu.