Pleochroism vs Color Change in Zultanite — Two Optical Effects, One Crystal

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Gem Article

Pleochroism vs Color Change in Zultanite — Two Optical Effects, One Crystal

Diaspore
5 min read Fact-checked 2026-04-27

Pleochroism and color change are two distinct optical phenomena that both appear in diaspore. Pleochroism (different colors visible from different viewing angles in the same illuminant) is caused by the orthorhombic crystal's anisotropic absorption along three principal axes. Color change (different colors visible from the same viewing angle under different illuminants) is caused by wavelength-selective absorption by trace chromophores. The two effects are independent and combine in cut diaspore.

The verified facts

This entry is part of the Zultpedia editorial archive on color-change diaspore from the İlbir Mountains of southwestern Türkiye. Mineral species: diaspore (α-AlO(OH)). Hardness: 6.5–7 Mohs. Refractive index: 1.682–1.752. Specific gravity: 3.30–3.39. The verified mineralogical baseline is documented across the property guides; the citations beneath this entry trace each claim to its primary source.

Editorial framing

Zultpedia treats color-change diaspore as a single-source mineral species first and a trade-name commodity second. The trade names Zultanite®, Csarite, Ottomanite, and Turkizite all refer to the same gem from the same locality; mineralogical claims apply equally to all four.

Cross-references

See also the related entries listed beneath this article and the property guides for verified physical and optical values.