As we wrap up our series on precious jewels, it is kind of fun to spotlight one last gemstone. One that isn’t immediately beautiful or desired. But it is the rarest! Discovered in east Asia by British mineralogist Arthur Pain, the so-called “Painite” gemstone can be found in several colors, and the various hues seen as light hits them give an uncommon view. Incredibly, only 25 such stones exist today, and the value per gram works out to $9,000! Despite the fact that...