ae 
64 Lieut. Ruggles on the Copper Mines of Lake Superior. 
tive positions of the zeolites, and their occurrence as incrustations 
on rocks, or as fillings of cavities or seams, and never in dissemi- 
nated crystals through the texture of the rock,—the green coating 
of the nodules, which is sometimes a carbonate of copper when 
there is native copper in the rock to undergo alteration,—the cor- 
respondence between the elements of the minerals and the com- 
position of the including rock, and at the same time their con- 
trast in being hydrous while the constituents of the latter are 
anhydrous,—and the known formation of zeolites in caverns,— 
these various facts appear to establish infiltration as the principal 
means by which amygdaloidal minerals have been produced. 
Art. VII.—Considerations respecting the Copper Mines of Lake 
Superior ; by D. Rueexezs, Ist Lieut. 5th Regt. U. 8. Infantry. 
Recentty I had the honor to communicate some particulars in 
relation to the copper mining region, as well as the discovery of 
a vein of black oxide of copper, tinged with the carbonates, near 
Copper Harbor. Now, I propose extending those views, accom- 
panied by observations touching collateral points, and deem it 
proper to recapitulate some of the circumstances connected with 
this discovery, as a basis for more extended observation.* It has 
already been stated, that the troops, while engaged about the 
middle of November last, in making some slight excavations, 
connected with the establishment of this post, found some bowl- 
ders of black oxide of copper of great density, richness and beau- 
ty, inducing an examination of a circuit of some fifty or sixty 
feet in diameter, from which some tons of bowlders, of uniform 
composition, were taken. (See fig. 1.) 
Description of Fig. 1.—A. Copper Harbor.—B. Lake Fanny Hooe.—C. Lake 
Martha Stevenson.—D. Lake Clara Geisse.—E. Fort Wilkins.—F. U.S. Mineral 
Agency.—G. Pittsburgh company’s cabins.—H. Main channel.—l. Centre reefi— 
K. Lake Superior—Q. Lake Anna Stannard.—L. Silicate of Copper.—m. Bowl- 
ders of black oxide.—n. Trap dykes protruding.—n!'. Mother trap range.—Scale 
of diagram, nearly two inches to the mile. 
* The present communication appears in a great measure to supersede the pre- 
vious one received Feb. 12, 1845. That paper, agreeably to the author’s wishes, has 
been forwarded to another destination. The historical fact, cited by him anterior 
to 1821, may be found in Mr. Schoolcraft’s memoir in Vol. II of this Journal, 
p. 202, with a figure of the large mass of native copper, now at Washington.—Eds, 
