Chrysocolla.-Handsome specimens are found in the Copper Falls vein, forming delicate stalactitic incrustations on the veinstone, and sometimes coating the crystals of analcime.

Chalcopyrite.-Veins of quartz containing this ore are numer ous in the trappean rocks of the Azoic series, in the neighborhood of Echo Lake, about 15 miles east of Saut St. Marie. Copper pyrites is the predominating ore at the Bruce and Wellington mines on Lake Huron: it has also been found in veins in the Huron Mts., on the south shore of Lake Superior, where no mining has yet been carried on.

Copper. The native metal is now the exclusive object of mining enterprise on Lake Superior, no veins producing ores being now worked, on either the north or the south shore. The sulphurets, however, are still mined on Lake Huron, in the Azoic rocks, a formation which has not been proved as yet on either shore of Lake Superior, to contain any workable vein of the

native metal.

The largest mass of copper yet discovered on Lake Superior was in the 10-fathom level of the Minnesota mine, on the socalled "conglomerate lode," or the copper-bearing vein which lies between the trap and a thin bed of conglomerate that runs through the mining ground, and which has been opened to a depth of between 80 and 90 fathoms without ceasing to produce largely. This mass was 46 feet long, and is said by the superintendent of the mine to have weighed about 400 tons: a single cut across it exhibited a thickness of six feet of pure metallic copper. This mass was estimated to contain at least 90 per cent of the pure metal. The operation of cutting it up lasted thirty months.*

Almost all the specimens collected on Lake Superior as crystallized copper, are, in reality, not actual crystals, but only imitative forms produced by juxtaposition with the crystalline faces of some mineral substance, and usually of calcareous spar. The large masses which are seen in collections, and labelled "crystallized copper from the Cliff mine," usually exhibit only a few indistinct planes which can be referred to the crystalline force of the metal itself.

The finest groups of crystals ever obtained in the copper region were from the Old Copper Falls mine, a locality which has long ceased to be worked; and no other has furnished any specimens to compare with those found here.

The predominating form in these groups was the rhombic dodecahedron; but the octahedron was not of unfrequent occur

* The size of the pieces into which the great masses are cut for convenient handling under ground and shipment is now much greater than it was formerly: block's of copper weighing from 8000 to 9000 pounds are not unfrequently brought to the surface and sent off to the smelting works.

rence. The diameter of the perfectly formed crystals rarely exceeded one-fourth of an inch, although single crystals from this locality, octahedrons, have been seen as large as an inch across their bases. The finest single crystals, as far as ascertained, are from the Cliff mine, and are tetrahexahedrons. One in my collection, considered by many the most beautiful crystal ever found in the Lake Superior region, is about three-fourths of an inch in diameter, and nearly perfect.

The occurrence of native copper as a pseudomorph after aragonite, reported by Söchling* as from Lake Superior, may with the strongest probability be set down as an error. It is very likely that the pseudomorph in question was from Corocoro, South America, where interesting ones of this kind do occur. There is a very great tendency to confusion in the localities of American minerals sent to Europe, as every mineralogist on this side of the water has learned by experience. No aragonite has ever been found in the copper region, as far as I know. Native copper, as a pseudomorph of calcite, has been noticed by me in a single instance, in a specimen from the Old Copper Falls vein.

The specific gravity of the native copper, sawn from the interior of a large mass of the chemically pure metal, has been previously stated in our Report at 8.838; this is lower than that given by Erdmann and Scheerert as the specific gravity of crys tallized copper. The specific gravity of the copper smelted at the furnace near Detroit was found to be considerably less than that of the native metal. A piece sawn from the centre of an ingot, and showing no signs of any air-bubbles, gave a specific gravity of 8-601; another portion of the same ingot taken from near the surface gave 8.570; both pieces appeared, under the magnifying glass, equally free from bubbles.

This copper, which was smelted from masses brought from the Toltec mine, was found on examination to be chemically pure, with this exception, that it contained T of silver, about seven ounces to the 2000 lbs.

Datholite.-Fine crystals of this mineral have been found only at the locality on Isle Royale, which has long since ceased to be worked, the island being now entirely deserted by all except a few fishermen. There are several localities on Keweenaw Point, however, where it occurs in great abundance, but not, so far as I have observed, in handsome crystallizations. The gangue of the Hill vein, on the Copper Falls location, consisted, in a portion of its more northern extension, of a greenish magnesian silicate penetrated, in every direction and sometimes forming a sort of breccia, with branches and strings of datholite. It is usually massive, translucent, highly vitreous in lustre, and of a light Pogg. Ann., civ, 832.

Erdmann and Marchand's Journal, xxvii, 194.

flesh-red color, owing to the presence of a minute quantity of suboxyd of copper diffused through it.

The veinstone of the Ontonagon region had seemed to be quite destitute of this mineral, and it was not until last summer that it was discovered by me in that district. At the Minnesota mine, among the vein-stuff thrown out, some singular nodules were observed looking like rusty cannon balls. On breaking one of these open and examining it, it was found to be datholite, in a singular and hitherto unobserved form.

The mineral is quite compact, breaking with a conchoidal fracture, perfectly white, opaque, and resembling in its physi cal character the purest and most close-grained marble. Its hardness = 45; specific gravity 2.983.

An analysis of this mineral by Prof. C. F. Chandler, gave the following results:

The quantity of datholite which is found on Lake Superior is very considerable, but it does not occur as a constant ingredient of the veinstone in any of the large mines now worked; and it is not probable that it will become of economical value for the extraction of the boracic acid it contains, however interesting it may be in a theoretical point of view, as connected with the origin of the cupriferous veins.

Hematite. The purity of the mountain masses of iron ore, which are now extensively mined at various points from 14 to 17 miles west of Marquette, may be inferred from the following analyses recently made of specimens from the three principal mines, or quarries, as they may more properly be called. The specimens are, indeed, selected ones; but an inexhaustible supply of ore of the same quality could be obtained, without rejecting any considerable amount of the stuff which is quarried out, were it desirable to ship a perfectly pure ore. The average yield of the ore shipped would, in point of fact, fall but little below that given by the following analyses.

I. is ore from the Jackson, II. from the Cleveland, and III. from the Burt or Lake Superior mountain. The fragments analyzed were, in each case, broken from the different portions of

the same large specimen, one object being to ascertain what the variations in the quantity of oxygen were, in different portions of the same mass. I. c. is the mean of three closely-agreeing determinations.

In the above analyses, the iron having been precipitated from the chlorohydric acid solution by ammonia, the filtrate was evaporated to dryness and ignited, and in no case did the residuum amount to more than a few hundredths of one per cent. In I. c. and III. b. there was a weighable quantity of lime present, amounting, in each case, to 0.05 per cent. It was not possible, in any instance, to obtain a weighable amount of alumina. The oxygen was therefore determined by the loss, as giving more accurate results than could be obtained by the process of reduction with hydrogen. It appears, therefore, that these ores are mixtures of the peroxyd with a minute and varying portion of the magnetic oxyd.

Both the Burt and Cleveland Mountain ores show minute crystals of magnetite scattered through their mass; in the Burt ore these crystals are from to of an inch in diameter; in the Cleveland, so small as to be hardly visible without a magnifying glass. No sulphur or arsenic could be detected in any of the specimens examined. The insoluble portion consists of silica, with only traces of lime, alumina and magnesia: this silica is partly in combination with the iron in the form of a silicate of iron, and partly present in the form of grains of quartz. On the whole, it may be said with truth that these ores surpass in purity any known to exist elsewhere in the world in anything like the same quantity.

Leonhardite. This mineral has been observed only in the Old Copper Falls vein, where it was very abundant; but a careful investigation would probably reveal its presence at other localities. An examination was made of this mineral to ascertain at what temperature it parts with a part or all of its water, with reference to H. Rose's investigations on Laumontite, which he has shown to lose a portion of this constituent at 100° C. The results gave on the mineral in small fragments:

The 146 per cent is probably not essential to the constitution of the mineral; the loss by ignition agrees well with the formula which takes the oxygen ratio of the bases and silica as 4:9, and 12 H.

Limonite.-This ore of iron has recently been discovered and for the first time on Lake Superior in any noticeable quantity.

It occurs at the Jackson iron mountain, where it forms beds of several feet in thickness, occupying depressions in the anhydrous ore, from the decomposition of which it may have been formed. The analysis gave the following results:

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 considered to aid in the reduction of the ore.

Manganite.-Handsome specimens of this mineral were given 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 noticed by T. S. Hunt (this Journal, [2], xix, 417), and afterwards more fully described in the Report of the Canada Geological Survey, 1853-6, p. 388. The result of my analyses, made two years ago, confirm entirely those already published by Mr. Hunt; the mineral, which appears homogeneous in composition, being in fact a mixture of the arseniurets of copper and nickel.

Two analyses of different specimens broken from the same mass gave as follows:

I.

II.

Specific gravity 7-527.

In II. the quantity of arsenic required to form with the copper 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 analysis 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