Occurrence
The rare mineral manganosite, found previously only at two localities in Sweden, was first identified in a single specimen in the laboratory collection of minerals at Harvard University. Nothing is known of the source of the specimen, which is a typical bit of granular franklinite-zincite ore that might have come from either Franklin or Sterling Hill. Mr. McGovern, of Franklin, told the author that he had seen considerable masses of an identical ore taken from the Taylor mine at Franklin, but that none of it was saved. The specimen therefore probably came from that mine. The occurrence of manganosite in the zinc ores is not surprising and is interesting as presenting manganous oxide in two crystalline phases in immediate contact—the isometric form in manganosite and the hexagonal in the zincite molecule which invariably contains some MnO.

In 1914 manganosite was found in place at Franklin in workings on the 900-foot level at the extreme north end of the mine. In this occurrence it is in large grains as much as an inch in diameter and in octahedral crystals, interspersed with strongly magnetic franklinite and coarsely bladed zincite. (See Plate 2, A.) The cleavage is prominent, but the color is masked by the blackish coating that marks the beginning of oxidation. Octahedral parting is also well developed in some of the specimens. The author is indebted to Mr. G. L. Morse, then of Franklin, for the first specimens of this discovery. The optical characteristics of this manganosite were studied by Ford (285).