Peel jicama and cut enough into 1/4-inch dice to measure 1/2 cup. In a food processor pulse dates to a paste and transfer to a bowl. Stir diced jicama, lime juice, scallion, and mint into dates and season with salt. Date mixture may be made 1 day ahead and chilled, covered. Cut remaining jicama into 1/4-inch thick slices and cut each slice into as many 1 1/2-inch triangles as possible. Jicama triangles may be made 1 day ahead, wrapped in damp paper towels, and chilled in a sealable plastic bag. Top jicama triangles with some date mixture and garnish with small mint leaves.