Frozen Lemon Berry Margaritas

6 lime wedges
3 tablespoons coarse sugar
2/3 cup lemonade concentrate
1 cup frozen unsweetened raspberries
2 cups ice cubes
1 (16 ounce) package frozen sweetened
    sliced strawberries, partially thawed
1/2 cup frozen blueberries
1 tablespoon sugar
1/2 cup tequila, optional

Using lime wedges moisten the rims of six margarita or cocktail glasses. Set aside limes for garnish. Sprinkle coarse sugar on a plate; hold each glass upside down and dip rim into sugar. Set aside. Discard remaining sugar on plate.

In a blender combine the lemonade concentrate and raspberries; cover and process
until blended. Press mixture through a fine meshed sieve; discard seeds. Return raspberry mixture to blender; add ice, strawberries, blueberries, sugar and tequila if desired. Cover and process until smooth.

Pour into prepared glasses. Garnish with reserved limes.