Final answer:
The sparkle of a diamond is caused by the effects of total internal reflection and dispersion. The precise cutting of the diamond's facets, making the diamond sparkle with flashes of brilliant color.
Step-by-step explanation:
The meaning of sparkle in the context of diamonds refers to the way light interacts with the facets of the gemstone. High-quality diamonds are known for their ability to transmit light with little absorption, appearing clear and colorless. However, these diamonds can exhibit a sparkle with brilliant colors when illuminated by white light due to a phenomenon known as total internal reflection coupled with dispersion.
Total internal reflection occurs because diamonds have a large index of refraction and a critical angle of only 24.4°. When light enters a diamond, it is reflected internally multiple times due to the specially cut facets that prevent light from easily escaping unless it makes an angle smaller than the critical angle. This causes the light to be concentrated and exit through fewer places, leading to the sparkling effect.
The colors seen emerging from a diamond when it sparkles are caused by dispersion, which is the separation of white light into its component colors. Although a diamond might appear colorless, the internal reflections and dispersion create flashes of color, adding to the gemstone's allure. Structural defects and inclusions can contribute to the color of certain diamonds, but the sparkle itself is a result of the diamond's optical properties and precise cut.