Black salt is salt darkened with charcoal, soot, scraped iron or black pepper, and it is used for protection, for banishing and for 'sending back' in a way that white salt is not. Its history in the Atlantic world is genuinely mixed: a dark salt appears in European household and witch-lore as a protective and cursing material, and it entered the American occult trade in the twentieth century, where it now sits on the same shelf as the hoodoo washes. In hoodoo it is a later and partly commercial arrival rather than one of the old materials, and the corpus records that rather than back-dating it.
It is laid in lines at doors and windows, added to a wash that is meant to clear a house of something unwelcome, carried in a packet, or used in a reversing work where the salt is meant to return rather than merely to bar. It is often paired with red brick dust - the red to hold the line, the black to turn what crosses it - and it discolours whatever it touches.
Black salt is the material most often detached from any tradition and sold as a universal 'witch supply', and its presence in a hoodoo entry is a record of that commerce rather than a claim that it was always there. The corpus marks the difference between a material a community made and a product a supplier invented, because blurring the two is how the traditions get homogenised.
Every entry that names Black Salt, grouped by the system it comes from.