The wedding ring signifies union, the circle, eternity. The diamond, a symbol of imperishable love. In medieval times, rings were used commonly as pledges of a bargain, a good-faith gesture. The popularity of diamonds as tokens of commitment arrived in the 15th century, when the Austrian Archduke Maximilian presented what's believed to be the first betrothal rock to his French fiance, Mary of Burgundy. The medieval Italians also favored diamonds which they believed were created from the fires of love.
Wedding rings are popular objects of superstition.
To cure a sty, rub the ailing eye with a wedding ring. To cure warts, prick them with a gooseberry thorn thrust through the ring. Turn a wedding ring three times and your wish will come true. By the way, the belief that a ring is worn on the third finger because a vein runs from there to the heart has been discounted scientifically. White is associated with purity.