Zultanite (color-change diaspore, 6.5–7 Mohs, RI 1.682–1.752, color-changing across three illuminants) and andalusite (Al₂SiO₅, 7–7.5 Mohs, RI 1.629–1.650, strongly pleochroic but not color-changing) are both trichroic but differ in mineral species, hardness, and the nature of their optical drama: Zultanite’s shift depends on light source, andalusite’s depends on viewing angle.

Mineralogy

Both gems require a thorough comparison across crystal system, hardness, refractive index, specific gravity, and optical character. See the property guides for the verified values on each axis.

Source and supply

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

Optical phenomenon

Color-change diaspore (Zultanite) and andalusite differ in the physics of their optical drama. Color change depends on illuminant; pleochroism depends on viewing angle.

Jewelry suitability

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