Gemstone
Zultanite
Zultanite is gem-quality color-change diaspore (α-AlO(OH)) mined exclusively from the İlbir Mountains of southwestern Türkiye. Suggested-retail prices range from USD 750 per carat for stones under one carat to USD 14,000+ per carat for stones above 20 carats — an order of magnitude less expensive than alexandrite while offering a comparable three-illuminant color shift between sage-green, champagne-gold, and raspberry-pink. This hub indexes every Zultpedia entry on the gem: how to identify it, how much it is worth, where authorized sellers are, how to verify a lab report, and how to care for the jewelry.
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Glossary Term
Culet
The pointed bottom tip of a faceted gemstone, where the pavilion facets meet. A pointed culet is structurally vulnerable; many modern cuts use a small flat "open culet" or rounded keel instead.…
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Glossary Term
Dispersion
The separation of white light into spectral colors as it passes through a transparent material, producing the "fire" visible in cut gemstones. Diaspore has moderate dispersion (~0.020), lower than diamond (~0.044) but…
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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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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.…