Although I follow facet designs I have begun to understand just how much gemologists vary on main angles. I just finished some math involving Snell’s law and the law of refraction. Things never quite follow theory in the real world so I am trying to expand my theory. I don’t understand the mathematics behind calculating dispersion. Today I also learned about the heart & arrow effect in diamonds, does the change in pavilion angles have the same effect on gems such as corundum? I still don’t fully understand gemstone design and how to fully take advantage of dispersion. Could anybody give some good personal input or share articles.