* Reflection: Light bounces off the surface of the jewel. A smooth, highly polished surface reflects light in a more organized way, creating a brighter, more defined reflection.
* Refraction: Light enters the jewel and bends as it passes from the air (or other medium) into the denser material of the gem. The amount of bending depends on the angle of incidence and the refractive index of the gem.
* Dispersion: Different colors of light bend at slightly different angles when they refract. This is called dispersion, and it's what creates the "fire" or rainbow-like flashes in gemstones like diamonds.
* Internal Reflection: Once inside the jewel, light bounces around off the internal surfaces. A well-cut jewel is designed to maximize internal reflection, keeping the light trapped inside and bouncing it back out through the top of the stone. This is what gives a jewel its brilliance.
* Color: Certain jewels have the chemical composition to absorb certain wavelengths of light, and reflect the remaining wavelengths giving the jewels their color.
* Luster: Luster describes the way light interacts with the surface of a mineral or gem. It's determined by the mineral's refractive index, transparency, and surface texture.
So, in summary, jewels shine because of their ability to reflect, refract, disperse, and internally reflect light, and the luster determines the quality of light reflected.