Rock Candy is a confectionary candy with sugar crystals. The first rock candy was invented India and Persia by Ghantewala Halwai of Dehli, the candy was called Misri. He first began selling Misri 1790. Rock candy takes 6-7 days and is formed by letting a supersaturated solution of sugar and water. The best way to make rock candy is to heat the water before adding the sugar, allowing for larger crystals.