Topic
Mineralogy
Mineralogy entries on Zultpedia document the species-level identity of color-change diaspore: chemistry (α-AlO(OH)), crystal system (orthorhombic), refractive indices, pleochroism, perfect cleavage on {010}, and the trace iron + chromium chromophore mechanism that produces the alexandrite effect. Sourced from primary mineralogical literature (Mindat, Mineralogical Magazine, Wikipedia’s peer-reviewed mineral pages) and the Hatipoğlu et al. 2010 İlbir Mountains study.
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Glossary Term
Alexandrite Effect
Alexandrite effect (also called color change) is the appearance of distinctly different colors in the same gemstone under different illuminants — typically daylight versus incandescent or candlelight. Named after the gemstone alexandrite,…
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Glossary Term
Biaxial Positive
An optical character of anisotropic gemstones where light travels at three distinct refractive indices (nα < nβ < nγ) along three principal optical directions, with two optical axes along which light behaves…
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Glossary Term
Orthorhombic
One of the seven crystal systems in mineralogy, defined by three mutually perpendicular axes of unequal length. Orthorhombic crystals exhibit pleochroism (three colors visible along the three axes), biaxial optical character, and…
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Glossary Term
Cleavage
The tendency of a crystal to split along specific planes determined by its internal atomic structure. Cleavage quality is described as perfect, distinct, indistinct, or absent. Diaspore has perfect cleavage on the…
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Glossary Term
Refractive Index
The ratio of the speed of light in a vacuum to the speed of light in a given material. In gemology, refractive index is one of the primary identification tools, measured on…
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Glossary Term
Specific Gravity
The ratio of a substance's density to the density of water at 4°C. For gemstones, specific gravity is a primary identification tool measured by hydrostatic weighing or heavy-liquid suspension. Diaspore has a…
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Glossary Term
Mohs Scale
A 1-to-10 ranking of mineral hardness devised by Friedrich Mohs in 1812, measured by which minerals can scratch which. Talc is 1, diamond is 10. Diaspore tests at 6.5 to 7. The…
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Glossary Term
Pleochroism
Pleochroism is the appearance of different colors when an anisotropic crystal is viewed along different optical axes under the same light. It is a property of the crystals internal symmetry, not of…
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Glossary Term
Color Change
Color change in Zultanite — also called the alexandrite effect — is the appearance of distinctly different colors in the same gem under different illuminants: sage-green under cool daylight (6500 K), champagne-gold…
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Glossary Term
Diaspeírō
Diaspeírō (διασπείρω) is an Ancient Greek verb meaning to scatter or to disperse. It is the etymological root of the mineral name diaspore, given by René Just Haüy in 1801. The reference…