Rosecut vs. Brilliant cut diamonds

The standard brilliant-cut of a diamond was established in 1919 as the optimal way in which light is refracted to display the “fire” within the stone - that alluring brilliance attributed uniquely to diamonds. The brilliant-cut diamond shape resembles a cone where the light is maximized inside the stone and returned through its flat top. Prior to this gem-cutting development, diamonds were typically cut to reflect light from the surface, like the rosecut diamond with its broad facets and flat bottom. The rosecut diamond resembles a dome and reflects light more subtly and softly - a romantic vintage alternative to the flashy brilliant-cut. 

Brilliant cut on left; rosecut on right.