| Metallic Iron. | Sulphur. | Phosphorus. | Silica. | |
| Typical Steel Ore | 9.24⅔ | .20⅔ | .03⅔ | 6.17⅔ |
| Lake Superior | 68.48 | —— | .053 | 2.07 |
| Iron Mountain | 65.500 | .016 | .040 | 5.750 |
| Snoqualmie | 68.808/13 | .0234/13 | .028⅔ | 2.6110/13 |
This showing places the Snoqualmie ores in the front rank of American steel ores; indeed, it shows a little higher in metallic iron, and a little lower in phosphorus, than any of the others. These analyses are, of course, made from the ore proper; i.e., without any addition of the matrix, or gangue-rock, in which the ores are imbedded. With all magnetites of this type it is only in exceptional spots that much of the ore can be gotten, free from the enclosing rock. Under ordinary circumstances something like 20 per cent. of the ore sent to the furnace will be gangue-rock. There is reason to hope, however, that ere long there will be a practical method for separating the rock from the ore, and at the same time getting rid of most of the sulphur. At Cranberry, N. C., the ore is now roasted and stamped into small bits, and an experiment has been made of passing the ore through a jigger, whereby the hornblendic and other enclosing rocks were separated by the pulsations of the water, as in coal washing.
Improved processes.The Lackawanna Iron and Coal Company, Pennsylvania, has been separating the ore from the rock with good results. The same has been done at Crown Point, N. Y., Lion Mountain, near Plattsburg, N. Y., Negaunee, Mich., and Beach Glen, N. J.
The process is really one of concentration, in some respects similar to that pursued with the refractory ores of the precious and base metals. The ore is first calcined sufficiently to make it friable. It is then crushed, by a Blake or other rock-breaker, and is finally sluiced, or jigged, or both. The aim is to produce a Bessemer concentrate which would yield 60 per cent. or more metallic iron, and at the same time get rid of whatever phosphorus might be in the gangue-rock. In the best experiments the object was more than accomplished. The concentrate contained 63 per cent. of metallic iron, the middlings 55 per cent., and the tailings 16 per cent. This experiment was made with a refractory Adirondack magnetite, which was so intermixed with hornblende, quartz, mica, etc., that the ore might be described as a hornblendic gneiss, carrying a large proportion of magnetite. No doubt experience will teach some way of saving the ore that is now wasted in the tailings.
Thus we may hope to see removed in a short time the only practical difficulty in working the crystalline magnetites, such as those of Snoqualmie, and many others.
Granite.III. Granite, Limestone and Marble.—What is here called granite is really syenite. It is found high on the mountains, associated, as already intimated, with the magnetic iron ore, and with hard quartzite, porphyry, epidote, hornblende, and limestone largely marbleized. This group of rocks forms the core of the Cascade Mountains, and hence underlies all the coal-bearing rocks to the westward. The group has been assigned by some geologists to the Archæan age; but it is possible that they are metamorphosed strata of the Silurian, or some subsequent period. Some of this syenite has a large proportion of quartz, which gives it a light appearance; but in other places the hornblende crystals are of good size and in full proportion, and the feldspar is of the orthoclase variety, which gives a mixture of three colors, and makes fully as handsome a stone as the Quincy granite.
Limestone is reported as existing in some of the islands in Puget Sound, where it is burnt into lime; but I have met with no particular account of it.
Marble and limestone.The limestone and marble associated with the iron ore on the Cascade Mountains has already been alluded to. It is of fine quality, very abundant, and easily quarried. It will have great value for flux and commercial lime. It is also beautiful in color, varying from the purest white to blue, and mixtures of the two colors. In texture it is sometimes exceedingly fine grained, and in others crystallized into a true and beautiful marble, which, so far as can be judged by eye, would be well adapted to both inside and outside finishing and statuary. On Mount Logan the limestone deposit almost covers the mountain above the lower line of the iron ore, and is so exposed as to be quarried with the greatest ease.
The same association of limestone in heavy beds with iron ore seems to exist also on the Cle-ellum, as mentioned by Mr. Burch. This gentleman spoke to me, also, of a very beautiful and easily burned limestone in the Wenatchie Valley. Large beds of limestone also exist in connection with the precious and base metals, which are next to be described. In the Colville country limestone seems to abound.
Precious metals on Cascade Mountains.IV. The Precious and Base Metals.—In the Cascade Mountains, and in the mountains north of the plateau country of East Washington, and in the Cœur d'Alene Mountains, within the border of Idaho, occur numerous veins bearing gold, silver, copper, lead, sulphur and iron. Discoveries on Cascade Mountain proper have been made on both sides, chiefly in the region of the iron ore. Those at the Denny and Chair Peak mines have been most spoken of. Professor Mason, of the "Rennselaer Polytechnic Institute," Troy, New York, gives the following assay of two samples sent from the Chair Peak claim of Kelly, Wilson & Co.: