- Lewes, Sussex, England, United Kingdom1
- Limoges, Haute-Vienne, Limousin, France1
- Little Piney, Pulaski County, Missouri, United States1
- Lockport, Niagara County, New York, United States1
- Lord Dudley's Mine, Dudley, West Midlands, England, United Kingdom1
- Louisville, Jefferson County, Kentucky, United States1
- Lubietova, Banskobystricky, Slovakia1
- Lycoming County, Pennsylvania, United States1
- Lyme Regis, Dorset County, England, United Kingdom1
- Magnet Cove, Hot Spring County, Arkansas, United States1
- Mansons Mine, Bucks County, Pennsylvania, United States1
- Maryland1
- Maryland, United States1
- Massachusetts1
- Matlock, Derbyshire, England, United Kingdom1
- McNamee Mine, Bath, Aiken County, South Carolina, United States1
- Mediterranean1
- Middletown, Middlesex County, Connecticut, United States1
- Midland, Cabarrus County, North Carolina, United States1
- Milos, Nisos, Cyclade Islands, Aegean Islands, Greece1