Brilliance, to borrow Nabokov’s description of human life, is a “brief crack of light between two eternities of darkness.” When we cut a diamond and give the rough crystal its shape, we also add facets. The facets are mirrors, facing all directions. Facets directed at us are bright; when facing away, they are dark. Brilliance is the constant flickering of facets between light and dark states when the diamond twirls. Even distribution of brilliance is the key to diamond’s health