Gemstone
Diaspore
Diaspore (α-AlO(OH)) is the mineral species, first described by René Just Haüy in 1801. While diaspore is geologically common in bauxite ore worldwide, gem-quality color-change diaspore — the alexandrite-effect variety sold as Zultanite, Csarite, Ottomanite, and Turkizite — is documented only from a single locality: the İlbir Mountains of Türkiye. Buyer prices range from USD 750 per carat to USD 14,000+ per carat depending on weight band and color-change strength. This hub indexes every Zultpedia entry on the species.
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FAQ Cluster
Zultanite Jewelry Care — Frequently Asked Questions
Zultanite jewelry requires gentler handling than harder gems. Clean only with warm soapy water and a soft brush. Never use ultrasonic or steam cleaners. Store separately from harder gems. Avoid daily-wear ring…
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FAQ Cluster
How to Identify Real Zultanite — Frequently Asked Questions
Identifying genuine color-change diaspore requires five tests: color change between daylight and incandescent illuminants, trichroic pleochroism via dichroscope, refractive index 1.682–1.752 with strong birefringence, specific gravity 3.30–3.39, and a recognized laboratory report…
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FAQ Cluster
Zultanite vs Other Color-Change Gems — Frequently Asked Questions
Zultanite (color-change diaspore) is one of several color-change gems on the market, each distinguished by mineral species, hardness, source region, and the strength and direction of color shift. Alexandrite (chrysoberyl) is the…
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Gem Article
Why Zultanite Has No Secondary Locality
Diaspore is geologically common — it occurs in every major bauxite deposit on Earth. Gem-quality color-change diaspore is not, because the simultaneous geological conditions required (slow metamorphic crystallization plus the specific iron-to-chromium…
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Gem Article
Pleochroism vs Color Change in Zultanite — Two Optical Effects, One Crystal
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…
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Glossary Term
Bauxite
A sedimentary rock composed primarily of three aluminum hydroxide minerals: gibbsite, böhmite, and diaspore. Bauxite is the world's primary aluminum ore. Most bauxite-hosted diaspore occurs as fine crystals of no gem interest.…
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Gem Article
Identifying Natural Versus Synthetic Diaspore
No commercial synthetic color-change diaspore exists in the gem trade as of 2026. Misidentification typically involves color-change synthetic sapphire, color-change garnet, or other-locality natural diaspore being sold under Türkiye trade names. Diagnostic…
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Glossary Term
Metamorphism
The process by which existing rock is transformed by heat, pressure, or chemically active fluids without melting. The İlbir Mountains diaspore deposit formed from regional metamorphism of bauxite-rich sediments under conditions favoring…
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Gem Article
How Master Cutters Orient Diaspore Rough
Master cutters orient color-change diaspore rough so the table facet is perpendicular to the direction of strongest color change while keeping the {010} cleavage plane parallel to the girdle (not the table).…
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Glossary Term
Asterism
The optical phenomenon of a star-shaped reflection appearing on the surface of a cabochon-cut gemstone, caused by light scattering from oriented inclusions. Asterism is not characteristic of color-change diaspore; the gem is…