What Makes A Diamond Sparkle ?
When you take a diamond outside when it’s sunny it will light up the whole surrounding area. However when you take it inside it will seem darker and not as brilliant. The diamond requires light entering into it such as the sun or an artificial light source.
The amount of light reflected (whatever the material) is related to the refractive index. Generally speaking the bigger the refractive index change the more light is reflected. So if you compare a diamond to a piece of glass cut into the same shape, the diamond will reflect more light and therefore it will sparkle more. The more a material bends light, the higher the RI Refractive index. Diamonds have a very high refractive index (about 2.42 compared to about 1.5 for glass).
The secret that diamonds hold regarding their brightness and diamond sparkle is inside a diamond and is a mix of light refraction, total internal reflection & dispersion.
Depending on how a diamond is cut the amount of light that refracts around the internal dimensions of the diamond before exiting through the crown varies. A well-cut diamond will refract the light several times before the light exits displaying sparkle, fire and scintillation. A diamond is specially cut with facets t give light optimal reflection.
A poorly cut diamond will allow the light to exit the diamond before it gets a chance to be refracted off the internal facets. As illustrated in the diagram’s – a diamond cut too shallow or too deep will not be as brilliant as a well cut diamond. Loyes Diamonds only sell diamonds with an excellent cut or a very good cut to ensure the highest levels of brilliance fire and scintillation.