[goldbux]

The face-centered cubic crystal allotrope of zirconium dioxide – known as cubic zirconia – looks to all [except the professionally trained eye] as a high quality diamond.

Cubic zirconia isn't cheap diamond.

Diamond is an expensive alternative to cubic zirconia.

Zirconium is essential as piping material inside nuclear reactors.

It's completely transparent to neutrons.

[Zr] cladding around the pipes containing fissile material in the reactor's core allows the chain reaction to proceed, throttled by control rods containing neutron-absorbing Boron [B].

[rodguy911]

We use zirconia in fishing rod guides as well for higher end guides.