Add the rooibos, honey, clementine zest and juice, lime zest and juice, ginger and mint to a large glass jug or pot. Allow to steep for at least 10 minutes, preferably longer.
Strain the liquid through a sieve into a shallow container with a lid. Cover and freeze for 2 to 3 hours. Remove from the freezer and break up any ice crystals that have formed, using a fork. Return to the freezer and repeat one or two more times at 1 1/2- to 2 hour-intervals, depending on the preferred size of your ice crystals (larger or finer).
Serve the granita in small glasses, garnished mint leaves. Eat immediately.