J, D. Whitney on Minerals of the Lake Superior region. 15 
It oceurs at the Jackson iron mountain, where it forms beds of 
several feet in thickness, occupying depressions in the anhydrous 
ore, from the sae ae which it may have been formed. 
The analysis gave the following results: 
Silica, - - + 6°54 
ron, - - - - - - 60°03 
Water, . . - - . 9°31 
Oxygen and traces of lime and magnesia, - 2412 
10000 
No sulphur or manganese could be detected; the original ore 
appears to have been only partially converted into limonite, as 
the quantity of water given by the analysis is considerably less 
than that required to form a hydrous peroxyd of iron. It is 
used at the Pioneer Furnace, near the Jackson Mountain, and 
me by Dr. G. H. Blaker, of Marquette, as having been procured 
in that vicinity; the exact locality is not known to me. 
Nickel and Copper, arseniuret of.—This is the same mineral no- 
Survey, 1853-6, p. The result of my analyses, made two 
years ago, confirm entirely those already published by Mr. Hunt; 
the mineral, which a \omogeneous in composition, being 
in fact a mixture of the arseniurets of ~~ and nickel. 
Two analyses of different specimens broken from the same 
mass gave as follows: 
i 
Arsenic (by loss), - 47°01 
opper, -  - 14:56 20°94 
Nickel, - . 33 35 31°24 
Silver, - - - - 
Gangue, - . a 57 
100-00 
Specific gravity 7°527. 
In 1. the quantity of arsenic required to form with the cop- 
per domeykite, and with the nickel copper-nickel, is 47-86 per 
cent, which agrees pretty nearly with that given by the analysis, 
The specimens obtained by me on Michipicoten island in 1853, 
are in coarsely crystallized calcite, and form nodules having a 
structure in concentric layers. The portions selected for se - 
is appeared perfectly homogeneous and had almost exactly the 
color and general appearance of copper-nickel. This ore was 
obtained in mining for silver on the island, from the trappean 
rocks; but on examining the excavations it did not appear that 
there was any regular vein of this or any other metalliferous 
mineral, the ore occurring in irregular nodules disseminated 
through the trap. There is little reason to believe that either 
