Old rock sugar, the color is usually pale yellow, mainly because of certain impurities in it caused by a relatively low purity.

Ordinary rock sugar, also known as monocrystalline rock sugar, has a higher purity, which is dissolved, purified and crystallized from white granulated sugar.

There are also differences regarding the preservation of the two. Old rock sugar, because of the many impurities in it, as well as the presence of molasses, is more susceptible to moisture.

Monocrystalline rock candy is also susceptible to moisture, but is relatively better. It is usually kept in a cool and ventilated place.