Zultanite shows color change (full body color shifts under different illuminants) while ametrine shows color zoning (purple amethyst and yellow citrine zones in the same crystal, both visible under any light). Both are quartz/diaspore hardness range (7 vs 6.5–7) but ametrine is single-source Bolivia, much less expensive, and shows zoning that varies by viewing angle than by illuminant.

Mineralogy

Each gem is identified by its mineral species, hardness, refractive index, and optical character. The verified values are documented in the property guides.

Optical phenomenon

The two gems compared here differ in the physics of their optical drama. Color change depends on illuminant; other phenomena depend on structure or viewing angle.

Source and supply

Where each gem is mined and how supply is structured determines availability and price stability.

Jewelry suitability

Hardness, cleavage, and toughness govern which gem suits ring-grade vs occasional-wear jewelry.