- Jihocesky, Bohemia, Czech Republic1
- Joplin, Jasper County, Missouri, United States1
- Juan de la Chico Mine, Guanajuato, Mexico1
- Jumilla, Murcia, Spain1
- Kings Creek District, Cherokee County, South Carolina, United States1
- Labrador, Newfoundland and Labrador, Canada1
- Lake Superior1
- Leadhills, South Lanarkshire, Scotland, United Kingdom1
- Lewes, East Sussex, England, United Kingdom1
- Limoges, Haute-Vienne, Limousin, France1
- Little Piney, Pulaski County, Missouri, United States1
- Livingston County, Kentucky, United States3
- Lockport, Niagara County, New York, United States1
- Lockport, Niagra County, New York, United States5
- London Grove, Chester County, Pennsylvania, United States2
- Lord Dudley's Mine, Dudley, West Midlands, England, United Kingdom1
- Lubietova, Banskobystricky, Slovakia1
- Lycoming County, Pennsylvania, United States1
- Magnet Cove, Hot Spring County, Arkansas, United States1
- Magnet Cove, Hot Springs County, Arkansas, United States4