Glossary

Alexandrite effect A reversible change of perceived colour with the light source, caused by the overlap of a… View term Birefringence The difference between a doubly-refracting gem's two refractive indices. Diaspore's is about 0.048 — high enough… View term Chromophore A trace element that gives a gem its colour. In colour-change diaspore the chromophores are chiefly… View term Cleavage A plane along which a crystal splits cleanly. Diaspore has perfect cleavage on the {010} plane… View term Colour-change diaspore The mineralogically correct name for the gem sold as Zultanite, Csarite, Ottomanite or Turkizite: gem diaspore… View term Csarite A second registered trade name for the same Türkiye colour-change diaspore, created after a dispute over… View term Diaspore The mineral species behind the gem — aluminium oxide hydroxide, α-AlO(OH), orthorhombic, first described in 1801.… View term İlbir Mountains The mountain region of Muğla Province in south-western Türkiye that is, to date, the only source… View term Mohs scale A 1–10 scale of scratch hardness. Colour-change diaspore sits at 6.5–7 — comparable to tanzanite or… View term Pleochroism The display of different colours along different crystal axes, seen as a stone is rotated in… View term Refractive index A measure of how much a gem bends light, used in identification. Diaspore's species range is… View term Specific gravity A gem's density relative to water. Diaspore is about 3.1–3.4 for the species, clustering near 3.39… View term Trade name A commercial label a seller applies to a marketable grade of a material (e.g. Zultanite). It… View term Zultanite A registered trade name for gem-quality colour-change diaspore from Türkiye. A commercial label, not a separate… View term