Galena is an ore of both lead and silver. It is found as veins in a variety of locations.
When galena ore is smelted, it will always produce one lead bar. There is also a 50% chance of a silver bar being produced.
Galena is also magma-safe, but just barely. Since galena is an ore however you'll probably want to use something else for magma management.
"Galena" is the name of the 6th month of the Dwarven calendar, covering late Summer.