Transparency is a function of wavelength/photon energy as well as the underlying material. Glass (the silica version) is opaque to portions of the UV spectrum.

Generally you'll get absorption (opacity) when the photon energy exceeds an energy gap, allowing valence band electrons to be bumped into conduction bands, creating a corresponding hole in the valence. In the case of metals, there is effectively no gap at points in k-space, so there is absorption throughout the spectrum.

I imagine a clever arrangement of atoms where non-metallic regions alternate with metallic ones could do the trick, as long as the transparent regions line up enough.

But anything this orderly doesn't look like a glass anymore.

For aluminum, you purify it, oxidize it, and then fuse it into a single crystal of corundum.

A hybrid alumina-silica glass can be created. The hybrid glass has a higher elastic modulus than other silica glass systems, and sheets of it can bend further before fractures form. This glass can be further toughened by creating it with high sodium content, then later exchanging the sodium ions with potassium ions. This type of glass is probably in your pocket right now.

Doped alumina-yttria hybrids are also useful in lasers.