German rock sugar is a form of unrefined sugar that is typically unprocessed, unbleached and resembles caramel-colored rocks in appearance. It is used primarily to sweeten tea, but it can be mixed into any food or beverage.
The origin of German rock sugar is in the region of East Frisia in the northwestern corner of Germany. The tradition is to place a piece of rock sugar, termed Kluntjes, in the bottom of a cup and then pour brewed hot tea over it, which melts the sugar and causes it to emit a crackling sound. One teaspoon of German rock sugar contains about 25 calories, making it higher in calories than granulated sugar at only 16 calories per teaspoon.