Glossary
Zultanite & Diaspore Glossary
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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
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
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
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
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
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
Crown
The upper portion of a faceted gemstone, above the girdle and including the table facet. Crown angles affect light return and the visibility of the gem's color through the table. For diaspore,…
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Glossary Term
Girdle
The narrow band that forms the widest perimeter of a faceted gemstone, separating the crown (top) from the pavilion (bottom). The girdle is where most jewelry settings grip the stone. For diaspore,…
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Glossary Term
Pavilion
The lower portion of a faceted gemstone, below the girdle. Pavilion facets reflect light back through the table to produce brilliance. Diaspore's strong birefringence (~0.048) makes pavilion facet edges visibly doubled when…
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Glossary Term
Table
The large flat top facet of a cut gemstone, oriented perpendicular to the optic axis in most faceted stones. For color-change diaspore, the cutter orients the table so that the table-up viewing…
