Final answer:
A clarity characteristic on the surface of a gemstone is known as a A. blemish. High-quality diamonds can sparkle with colorful lights due to total internal reflection and dispersion, which are enhanced by the gem's large index of refraction and precisely cut facets.
Step-by-step explanation:
A clarity characteristic confined to the surface of a polished gemstone is called a blemish. In constrast, an inclusion refers to a characteristic within the gemstone itself. Blemishes include scratches, nicks, and pits found on the gem's surface. Understanding the clarity of a diamond is crucial as it affects the gemstone's value. When a high-quality diamond is illuminated by white light, it can sparkle with flashes of brilliant color due to its specific physical properties.
The scintillating effect seen in diamonds arises from total internal reflection coupled with a large index of refraction. The critical angle for diamond-to-air surface is quite low, making light's escape less likely once it enters the gem. The numerous facets on a diamond are precisely cut to enhance this effect. The dispersion of light within the diamond breaks apart white light into its constituent colors, causing the diamond to display a colorful sparkle. This property, along with the gem's exceptional clarity, allows multiple internal reflections that concentrate the light and create a bright sparkle.