Add to ORKGThe Nigger Hill District, located on the Wyoming-South Dakota border in the northwestern Black Hills, is an area of Paleozoic sedimentaries, dipping outward from a central core of various alkaline and sub-alkaline Tertiary intrusive, and pre-Cambrian pegmatitic granite and schists. The Tertiary igneous rocks are of interest for three reasons: (1) they may furnish data that will contribute to the much debated problem of the origin of alkaline rocks; (2) when their structural relations are better understood, it will be possible to interpret more correctly the mechanics of their intrusion and the type of intrusive body they represent; (3) apparently they have been the source of the gold in a rare genetic type of potential ore deposit