When buying grapes, look for ones that are plump and firmly attached to the stems, and have smooth unbroken skins.
Rinse rice in a sieve until water runs clear. In a medium saucepan, heat 1 tablespoon olive oil over medium-high heat. Add curry powder; cook 30 seconds. Stir in rice, 2 1/2 cups water, 1 teaspoon salt, and 1/4 teaspoon ground pepper.
Bring to a boil; reduce heat. Cover; simmer gently until rice is tender and has absorbed liquid, about 1 hour. Remove from heat; steam, covered, 10 minutes.
Fluff rice with a fork; transfer to a shallow bowl. Stir in lime juice and remaining tablespoon olive oil; season with more salt and pepper. Refrigerate until cool, about 1 hour.
Stir in grapes, mint, and cashews.