"Rock sugar" redirects to hereRock candy (also called rock sugar) is a type of confectionery mineral composed of relatively large sugar crystals. This candy is formed by allowing a supersaturated solution of sugar and water to crystallize onto a surface suitable for crystal nucleation, such as a string, stick, or plain granulated sugar. Heating the water before adding the sugar allows more sugar to dissolve thus producing larger crystals. Crystals form after 6–7 days.