01

What to look for

With the naked eye and loupe: a glowing light effect that appears to float below the surface and moves as the stone is tilted. Moonstone shows a blue or white rolling glow; labradorite flashes spectral colors.

02

What it means

These optical effects are caused by light interference between alternating microscopic feldspar layers. They are optical phenomena rather than classic inclusions — included here as gem-defining internal features of feldspar gems.

03

Expert move

In moonstone, blue adularescence on a near-colorless body is prized. In labradorite, broad full-spectrum play of color is desirable.