Zircon

Uniaxial (+)
no = 1.924-1.960
ne = 1.968-2.015
δ = 0.044-0.055
Mitamict zircons tend to have lower birefringence (sometimes even isotropic).

Thin section pictures:

Zircon in peralkaline granite, Kola peninsula. Zoom 200x, XPL