Gray lead sulfide (PbS), the chief ore mineral of lead. One of the most widely distributed sulfide minerals, it occurs in many types of deposits and in many localities. In the U.S., galena is mined principally in the Mississippi River Valley. Galena often contains silver and so is often mined for that metal as well as for lead. Other commercially important minerals that frequently occur in close association with galena are antimony, copper, and zinc.