Glossary
Colour change
Some gemstones show a different colour depending on the light source. The best-known example is alexandrite: greenish to bluish in daylight, reddish to purple under warm incandescent light. Sapphire, garnet and spinel can also change colour. Laboratories record both colours – «colour in daylight» and «colour in incandescent light». The more distinct the change, the more sought after the stone.
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- GlossaryAbsorption spectrumWhen light passes through a gemstone, the stone absorbs certain wavelengths – the rest make up its colour.Read more
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Updated 2026-10-06