Since its discovery by a teenager in 1859, thousands of specimens of lustrous black tourmaline crystals from Pierrepont, New York, have found their way into both museum and private mineral collections worldwide. Pierrepont is a classic American mineral locality and a popular site for field collecting, and the discovery of new collecting sites there in the past decade has only enhanced its importance. Yet no detailed scientific research has been published until now. The six authors represent a team with comprehensive skills to tackle this study, which covers the locality's history, geology, and mineralogy. The origin of the mineralisation, the true nature of the black tourmaline, and the extensive suite of accessory minerals are presented in detail. The authors also resolve identification questions about the tourmaline and its many accessory minerals.