Glossary
Zultanite & Diaspore Glossary
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Glossary Term
Facet
A flat polished surface on a cut gemstone, geometrically arranged to maximize light return and color display. Color-change diaspore is typically faceted in oval, cushion, pear, or emerald cuts oriented so the…
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Glossary Term
Cabochon
A polished but non-faceted dome-shape cut, typically used for opaque or asterism-bearing stones. Color-change diaspore is rarely cut as cabochon because the alexandrite effect is most visible through facet returns. Cabochon-cut diaspore…
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Glossary Term
Inclusion
Any solid, liquid, or gaseous material trapped inside a crystal during its growth. Inclusions in gem-quality diaspore are typically minute negative crystals, two-phase fluid inclusions, and rare boehmite or chlorite needles. Inclusion…
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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…
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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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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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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
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
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
Birefringence
The difference between the highest and lowest refractive indices of an anisotropic gemstone. High birefringence produces visible doubling of pavilion facet edges when the gem is examined through the table. Diaspore has…
