Abstract

The discovery of a new locality for bravoite (Ni, Fe) S 2 has provided material for a study of this rare nickel-iron sulphide and has established the Missouri occurrence as the first in North America. The minuteness of grain size and the manner of the occurrence with pyrite precludes any determination of the optical, chemical or physical properties of the mineral. Nevertheless the remarkable zonal structure and the violet color which it exhibits in polished section agrees with that described from Mechernich, 3 Germany, and serves very well to establish its identity. Certainly, without the aid of the metallographic microscope and its accessories for high magnification, this mineral would have gone unrecognized and chemical assays would have established the pyrite merely as nickeliferous.

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