To a cocktail shaker add blackberries and jalapeno slices. Using a muddler or wooden spoon, thoroughly mash up the blackberries. Add the tequila, cointreau, fresh lemon juice, pickled jalapeno juice. Add ice and shake vigorously until chilled, about 2 minutes.

Spread out a layer of kosher salt, about a tablespoon onto a small plate. Take a lemon wedge and run it around the rim of glass. Dredge in salt to rim the glass, moving glass around evenly coat glass. Fill glass ice and strain the margarita into the glass. Garnish with additional lemon wedges and pickled jalapenos.