Diamonds get their brilliance from three things: reflection, refraction and dispersion. ... Only a portion of the light hitting a diamond is reflected; the rest travels through it. As the light moves through the diamond, it is scattered and fractured, creating the sparkle that diamonds are known for.

Does diamond reflect?

ilovebutter/Flickr The way that diamonds reflect light is unique: Inside the stone, the diamond will sparkle gray and white (known as “brilliance”) while outside of the gem, it will reflect rainbow colors onto other surfaces (this dispersed light is known as “fire”). ... “They do sparkle, but it's more of a gray color.

Do real diamonds refract light?

Diamonds are so sparkly because of the way they refract and bend light. Glass, quartz, and cubic zirconia may mimic a diamond's brilliance, but they have much lower refractive indexes.