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Gemstone Encyclopedia
When "Ceylon Sapphire" Does Not Mean What the L...
Why Ceylon sapphire is a trade descriptor rather than a formal origin or mineral variety, and how that affects sapphire identification and gemological reporting.
When "Ceylon Sapphire" Does Not Mean What the L...
Why Ceylon sapphire is a trade descriptor rather than a formal origin or mineral variety, and how that affects sapphire identification and gemological reporting.
Why Sardonyx Is Not a Mineral Species but a Lay...
Sardonyx is a layered chalcedony variety, not a mineral species. Learn why its name is a trade term, how its bands form, and what that means for identification.
Why Sardonyx Is Not a Mineral Species but a Lay...
Sardonyx is a layered chalcedony variety, not a mineral species. Learn why its name is a trade term, how its bands form, and what that means for identification.
Akoya Pearls and the Direction-Dependent Face o...
Akoya pearls change appearance with orientation because nacre is a curved, layered composite. Learn how luster, overtone, orient, and nacre thickness produce direction-dependent effects.
Akoya Pearls and the Direction-Dependent Face o...
Akoya pearls change appearance with orientation because nacre is a curved, layered composite. Learn how luster, overtone, orient, and nacre thickness produce direction-dependent effects.
Snowflake Obsidian and the Identification Probl...
Why snowflake obsidian is difficult to test for treatments: amorphous glass structure, cristobalite patterns, refractive index limits, and how coatings, dyeing, and fillers complicate gemological identification.
Snowflake Obsidian and the Identification Probl...
Why snowflake obsidian is difficult to test for treatments: amorphous glass structure, cristobalite patterns, refractive index limits, and how coatings, dyeing, and fillers complicate gemological identification.
How Iridescent Ammolite Gets Its Color—and Why ...
How ammolite's layered fossil shell creates interference colors, why orientation controls what is seen, and why cabochon cutting preserves and displays the iridescence.
How Iridescent Ammolite Gets Its Color—and Why ...
How ammolite's layered fossil shell creates interference colors, why orientation controls what is seen, and why cabochon cutting preserves and displays the iridescence.
Distinguishing Natural Mahogany Obsidian from A...
Learn how gemologists distinguish natural mahogany obsidian from manufactured colored glass using bubbles, flow banding, crystallites, surface features, and instrument-based testing.
Distinguishing Natural Mahogany Obsidian from A...
Learn how gemologists distinguish natural mahogany obsidian from manufactured colored glass using bubbles, flow banding, crystallites, surface features, and instrument-based testing.