No. It is a type of crystal.

yes it is not a metal, but a crystal

Ionic. Crystal structures are formed by ionic bonds and metallic bonds are, well, between metals.

Crystal Radii is also known as "Metallic Radii ". It is defined as "half the distance between the nuclei of two adjacent metal atoms in the metallic closed packed crystal lattice". It is used for metal atoms which are assumed to be closely packed spheres in the metallic crystal. As for ionic radii .... I don't know.

Hg, Cu, Fe, W