The Black Hills region is one of the most remarkable mineral areas of the world because it comprises within its limited area not only a great variety of minerals, but also an abundance of rare species, some of which are not known elsewhere. Articles describing these minerals are scattered through different scientific journals inaccessible to the greater part of the people of the state. These deal only with some of the rarer minerals, or in the more strictly eco nomic and geologic discussions give no more than mere men tion to the great majority of species.