Make sure to strain the pureed blackberry mixture to get rid of seeds and it will be a wonderful addition to minty fresh tea or lemonade. Brewed mint tea can substitute for black tea and fresh mint leaves in this refreshing drink.
Place tea bags and mint in a heat-proof pitcher. Add boiling water. Steep at least 10 minutes. Strain into another pitcher and discard mint and tea bags. Stir in sugar. Purée blackberries in a blender or food processor; strain through a fine sieve. Discard pulp and seeds. Stir blackberry purée into tea. Taste and adjust sugar as desired. Chill.
Serve over ice garnished with mint leaf and 2 or 3 blackberries.