Olive oil produced by stone mills is generally milder and more buttery-tasting, which some consumers, especially those who are new to the olive oil world, tend to prefer. Part of this softer taste profile is due to the fact that they contain less antioxidants. Another reason is that milling stones do not pulverize the olive skin, as some older model metal crushers do, so less chlorophyll is released -- in some cases, this is a enough of a disadvantage that some producers add leaves with the olives to get a more grassy taste.