248 F. A. Genth’s Contributions to Mineralogy. 
has, however, not been observed since in its pure state. The 
localities Phoenix and Vanderburgh mines, mentioned by Otto 
Dieffenbach, are extremely doubtful, the specimens, which came 
to my notice from there, were only tarnished chalcopyrite; the 
Barnhardt mine has proved to be worthless, and is exhausted, 
whilst the ores from the Pioneer Mills mine, which I have from 
time to time obtained, were mostly the mineral mentioned in my 
paper, Am. Jour. Sci. [2], xix, 18, as containing about 40 p.c. of 
r, or mixtures of chalcopyrite and barnhardtite with cop- 
perglance, which latter could be easily distinguished with a good 
magnifier in small veins, running through the whole mass, 
the above mentioned 40 oz. copper ore, barnhardite and erubesite, 
whilst the crust is chiefly composed of sesquioxyd of iron. 
5. Gersdor fite. 
I have observed this mineral on a specimen of anglesite from 
Phoenixville, Pa., on which it forms an incrustation ne par- 
tially decomposed galena and zincblende, associated wit 
chalcopyrite and covelline. The very small crystals are cubes 
with octahedral planes and, very rarely, those of the pentagonal 
dodecahedron, the latter frequently indicated by the striation of 
the cubical planes. B.B. it gave the reactions of sulphur, arseni¢ 
and cobalt; a nitric acid solution, however, showed the presence 
of a larger percentage of nickel than cobalt. 
6. Molybdate of Iron. 
I am indebted to Dr. D. D. Owen for some fragments of this 
mineral from Nevada City, California, and have made a few eX- 
periments with the same, but regret that the rarity of this sub- 
stance prevented a fuller examination. That which could be 
scratched off the quartz was not quite pure and contained a trace 
of limonite. Dilute ammonia acted readily upon it and extracted 
ail the molybdic acid, leaving behind the hydrated sesquioxyd 
of iron of a brown color. The sample examined gave 243 p. © 
