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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Glossary Term
Chromophore
The atomic or molecular structural feature responsible for a material's color. In gem-quality color-change diaspore, the chromophores are trace iron (Fe³⁺) and chromium (Cr³⁺) substituting into the aluminum site of the diaspore…
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Glossary Term
Optic Axis
A direction within an anisotropic crystal along which light travels without splitting into two rays. Biaxial gems like diaspore have two optic axes. The cutter orients the gem so the optic axes…
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Glossary Term
UV-Vis-NIR Spectroscopy
Ultraviolet-visible-near-infrared absorption spectroscopy. The standard laboratory technique for quantifying which wavelengths a gemstone absorbs and which it transmits. Color-change diaspore shows characteristic Fe³⁺ absorption near 425 nm and a broad Cr³⁺-related band…
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Glossary Term
Lustre
The character of light reflected from a gemstone's polished surface, ranging from dull through vitreous (glass-like) to adamantine (diamond-like). Diaspore shows a vitreous to subadamantine lustre when polished, related to its refractive…
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Glossary Term
FTIR Spectroscopy
Fourier-transform infrared spectroscopy. A non-destructive technique that identifies a mineral's molecular fingerprint via its mid-infrared absorption bands. For diaspore, FTIR confirms the species via characteristic O-H stretching modes, distinguishing it from chemically…
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Glossary Term
Fluorescence
The emission of visible light by a material when stimulated by ultraviolet radiation. Diaspore is generally inert to long-wave UV and may show weak yellow-green fluorescence under short-wave UV in some specimens.…
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Glossary Term
LA-ICP-MS
Laser ablation inductively coupled plasma mass spectrometry. A trace-element fingerprinting technique used in modern gemological labs to attribute a stone to its geographic origin by measuring parts-per-million levels of dozens of elements.…
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Gem Article
The Absorption Spectrum of Color-Change Diaspore
Color-change diaspore from the İlbir Mountains shows a characteristic UV-Vis-NIR absorption profile dominated by trace iron (Fe³⁺ band near 425 nm) and trace chromium (Cr³⁺-related broad absorption centered near 580 nm). Transmission…
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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…