Wiktionary
rock sugar
n. white sugar that has been crystallized into chunks
Wikipedia
Rock Sugar (band)
Rock Sugar is a Los Angeles-based band known for their mashups of pop music and heavy metal from the 1980s.
Usage examples of "rock sugar".
I think he'd enjoy some of the rock sugar, or maybe some of the sugar sticks.
Now, as his host poured chrysanthemum tea sweetened with rock sugar into their cups, and three fingers of whiskey into the glasses, Peter Ng fought for control.
She nodded, spooning brown crystals of rock sugar into the tan foam atop her coffee glass.