Jamboree Menthol Crystals, 100g [100% Pure, Plant-based, Cooling & Refreshing] Menthol Crystals are obtained from corn mint, peppermint and pennyroyal. Appearance: It is a waxy, crystalline substance, white in color. Use for refreshing flavour, to combat bad breath or mix in mouthwash and toothpaste. Make homemade candies and flavour them with menthol crystals to get a cooling effect.