The French are considered crude and overly sexual by the British, and Yorick seems to attribute their general lack of character to this habit. This theme of metal and mettle is a central one for Yorick, who perceives emotion as a thing of highest value. Later on in the narrative, he witnesses a beggar who begs only from women, and who never fails to get some money from them. Yorick is fascinated by this puzzle, and is restless with trying to work it out in his mind. The philosopher's stone was a legendary substance sought by alchemists, and said to be the secret ingredient in the process of turning lead into gold.
Gold is more valuable, but also more easily shaped into whatever one desires.
The shaping, here, is clearly evocation of emotion. To evoke emotion from others is to vindicate one's sense of personal worth and importance, and also influence the actions of others. That which is of value inspires desire, and Yorick, by envisioning women's emotions as golden, opens them up to desire, and all of the desperate, immoral action it can generate. Emotion is also of value to Yorick as a personal experience. This is very clearly elaborated in a tangential story he tells regarding a Marquis who falls on hard times.