Salt for the doorway, not the table
Sal negra is a coarse black salt, in a 2 oz or a 6 oz bag. It is a ritual salt and lives apart from the kitchen. It is not a cooking salt, and it is not the Indian black salt called kala namak.
In folk custom it is laid along doorways and windowsills, or sprinkled on the floor and swept out the door with the broom. Some people carry a little in a pouch or keep a pinch in the car. The 6 oz bag holds three times the salt of the 2 oz one, for when the custom is a regular part of your house.
In YERBERO herbs and teas, Sal negra is filed under S in the herbolario A–Z, next to Atado de salvia blanca.