For the blackberry-lime ice cubes: Add the frozen blackberries, lime zest and juice and Orange Simple Syrup to a blender and puree until smooth. Pour into an ice cube tray with sixteen 1-ounce wells, put on a baking sheet and freeze until solid, at least 2 hours.
For the blackberry-lime margaritas: Put 2 tablespoons sugar onto a small plate. Run a lime wedge around the rim of a rocks glass and dip the rim into the sugar to coat. Repeat with the remaining lime wedges and sugar with 3 more rocks glasses.
For each drink, put 4 blackberry-lime ice cubes in a blender with 2 ounces silver tequila and 1 cup regular ice and blend until smooth. Pour the margarita into one of the prepared glasses. Repeat with the remaining ingredients. Garnish each glass with fresh blackberries and a lime wedge.
Special equipment: an ice cube tray with sixteen 1-ounce wells
Orange Simple Syrup:
Make the simple syrup by combining the sugar, orange zest and juice and 1/2 cup water in a small saucepot. Heat over medium-low heat, stirring, until the sugar has completely dissolved, 3 to 4 minutes. Set aside to cool.