Among a number of specimens which the senior author (J. l)rugman) obtained some years ago from the widow of a mine manager, Mr. Legrand, of Belgian nationality, was one of massive blendc from the Flor de Peña mine, Lampazos, Nuevo Leon, Mexico, which carried a small quantity of a bright yellow, transparent substance that could not be identified with any known mineral. Goniometric and optical examination showed it to be monoclinic, but the material was mainly massive radiating-prismatic, and the few freely developed crystals gave only very approximate measurements (see table II). A chemical analysis by the iunior author showed it to be indeed a new mineral, a basic zinc arsenate, and the name ‘legrandite’ is proposed for it in recognition of the collector. The larger part of what remains after investigation of the small specimen has been presented to the British Museum for preservation in the mineral collection.