Mix sugar with a pinch of activated charcoal on a small plate to make a grey color.
Rub half a lime around the rim of a short glass and roll it in the sugar mixture. Set aside.
In a cocktail shaker, muddle 3 blackberries.
Add tequila, orange liqueur, fresh lime juice, and activated charcoal powder to the shaker.
Fill the shaker with 4-5 ice cubes, close the lid, and shake for 30-60 seconds until frosty.
Add fresh ice to the rimmed glass, strain the margarita into it, and garnish with 3 blackberries on a cocktail pick. Enjoy!