Zultanite shows strong trichroic pleochroism: it displays three different colors when viewed along its three principal crystallographic axes. Typical pleochroic colors are kiwi-green, dark green-brown, and pinkish-orange. This is independent of the color-change effect (which is driven by illuminant) — pleochroism shows three colors simultaneously, viewable through a dichroscope.

What pleochroism is

In anisotropic crystals (those without cubic symmetry), light traveling along different crystal directions encounters different absorption profiles. The result: the same crystal looks different colors when viewed from different angles. Diaspore is orthorhombic, so it has three principal optical directions — and three pleochroic colors.

Pleochroism vs color change

Color change happens when illuminant changes (the crystal stays still). Pleochroism happens when viewing direction changes (the illuminant stays still). Zultanite shows both effects — making it one of the most optically active gem species in the trade.

How master cutters use pleochroism

The cutter orients the rough so the most desirable pleochroic color appears through the table facet. For Zultanite, this typically means table-up to display the strongest green-to-raspberry color change while masking the dark green-brown axis at the pavilion.

Diagnostic identification

Strong trichroic pleochroism with these specific colors is a primary identification feature for diaspore. Few other gems show this combination — alexandrite is also trichroic but with different color triplets.