The Old Mine cut revolutionized the way diamond cutters viewed brilliance in a diamond In the 19th century, the Old European cut improved on a few subtleties of cutting to produce an even brighter stone.
In this new cut, we see the squarish profile approach roundness. Pavilion depth is reduced slightly and many of the facets are elongated to direct more light back up through the table. Crown facets are re-proportioned and distributed evenly around the table.
The improved symmetry and revised facet proportions all work together to direct more of the light through the top of the stone where we observe the brilliance and fire we have come to expect from a well cut diamond. Much of the dispersion, or fire, is retained.
Old European is one of my personal favorites. To use wholly unscientific terms, no other diamond cut I have encountered spits so many rainbows. My own wedding ring is set with Old European cut diamonds. I like to gaze into them and get lost in the shimmering colors. Further innovations have improved the light return, but none break up light into spectral colors quite like this.
Next time, we meet Mr. Tolkowsky.