Sprinkle a layer of coarse salt on a plate. Take six glasses and dip the rims in a shallow dish of water, then into the salt. Set side.

Add the blackberries, tequila, Grand Marnier, lime juice, simple syrup, and ice to a blender. (If serving on the rocks, do not add the ice!) Blend until smooth.

Pour into your margarita glasses and garnish with a lime wheel and a blackberry on a bamboo skewer. Serve immediately.