01

What to look for

Under 10x loupe in immersion: bands or patches of deeper or lighter color arranged inside the crystal. In corundum, bands often follow crystal geometry. In quartz, amethyst may show tiger-stripe zoning.

02

What it means

Color zoning helps identify natural growth, treatment, and sometimes synthetic origin. In corundum, straight angular bands are typical of natural growth; curved bands can indicate synthetic flame-fusion material or treatment-related features.

03

Expert move

Immerse the stone in water or immersion liquid to reduce surface reflections before examining zoning.