Spread the black salt in a layer in a flat dish. Pour some water in another flat dish just deep enough for the rims of the glasses. Dip the rims first in the water and then in the black salt, turning to coat the entire rims.
Add 2-3 ice cubes to each glass.
Combine the tequila, Blue Curacao and lime juice in a blender or in a covered mason jar that you can shake, shake, shake. Pour the mixture carefully over the ice so the salted rims stay intact. Serve the drinks immediately.
If you want, put the glasses in the freezer for a minimum of 30 minutes to get them really cold for your drinks!