An old word for the black capsules that medicinal speed came in. Back when speed came in these little black capsules, they were sometimes called Black Beauties. In the South, they were also known as Black Mollies. The capsules resembled the small fish known as the Black Molly. Ask someone from the South what black beauties are and they'll say "oh, black mollies."
Back in the old days, you could get black mollies. Purer than meth.