do diamonds shine or sparkle

With transparent diamonds, this does not matter as much. But when it comes to colored diamonds such as yellow or pink, the surface affects the wavelength that enters the gem. That will affect it - but it will not drastically change the appearance of your diamond. See Also: Do Black Diamonds Reflect Light And Sparkle?

Cut refers to how well a diamond's facets interact with light, resulting in their level of sparkle. A stone's facets will be measured to examine brightness (internal and external white light reflection), fire (the scattering of white light into the colors of the rainbow), and scintillation (the amount of sparkle a diamond produces).

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