We shall probably never know when the first diamond dealers were discovered, but we do know that, from ancient times until the eighteenth century, all the worlds ideal cut came from India.
Usually the engagement rings rough will be cut into whichever shape that requires the least amount of sacrifice. Marquise and oval shapes should have a length thats exactly twice the size of the width. If they are too narrow or too wide, the stone will loose light and appear too dark.
diamond dealers is Forever if you are just beginning your engagement ring search, or if you just want to purchase diamond jewelry as a personal gift.