for its abandonment is not known. The result of explorations by test pitting indicates that the quantity of ore present in the vicinity is large.

References: N. J., 1873, p. 89; 1879, p. 90; 1880, p. 129.

Deposits of limonite ore are known to occur at many other points in the limestone valleys between the Highlands ridges, but so far as known, explorations to test their extent have been carried on only at the localities described above. The positions of many other deposits are indicated in the old county maps of Warren, Hunterdon and Morris counties.

CHAPTER IV.

HEMATITE.

CONTENTS.

General discussion.

Character of the ore.

Appearance.

Composition.

Occurrence.

Localities.

Description of individual mines.

Cedar Hill mine.

Simpson mine.

Andover mine.

Byerley openings.

Marble Mountain mine.

Cooley's mine

Nolf farm exploration.

Titman shaft.

GENERAL DISCUSSION.

CHARACTER OF THE ore.

Appearance. The ore known as "red hematite" is composed essentially of the mineral hematite which is the oxide of iron represented by the formula Fe2O3. Though very different in its appearance when obtained from different localities, the variety that occurs in New Jersey is practically all of the same kind. It is a mediumly fine-grained aggregate of dark gray or black scales and thin plates arranged in a generally parallel position, thus producing a mass with a schistose structure. Because of the glistening of the little plates caused by the reflection of light

from their flat surfaces, this type of ore is frequently known as specular ore. In a few places the New Jersey ores lack the strongly pronounced schistostity. They are then black, finely granular aggregates with a dull luster.

The red hematite is easily distinguished from the brown hematite, or limonite, by its crystalline character, its black or darkgray color, and by the fact that it does not yield any appreciable quantity of water when strongly heated. It differs from magnetite in possessing a red streak or powder and in being nonmagnetic. Although the most valuable of all the ores of iron in the United States, it is comparatively unimportant in New Jersey. It has been found at about half a dozen localities, but has been mined with profit at only one.

Composition. Theoretically, hematite contains 70% of iron, but the ore as marketed rarely assays more than 65% of the metal. The impurities are usually quartz, apatite, and the minerals characterizing the rock with which the ore is associated. No accurate analyses of the New Jersey hematites are available. It is probable that their principal impurity is quartz and chlorite or some other magnesian silicate.

OCCURRENCE.

The occurrence of the hematites in New Jersey is practically confined to the quartzite conglomerates and shaly rocks associated with the Franklin limestone. The geological relationships are not clear. In some places the hematite appears to form the matrix of quartzites, at other places to impregnate the shaly rocks and at one place it occurs as a vein-like or dike-like mass cutting across the schistosity of certain shaly rocks that resemble sheared volcanics. In all cases it appears to be subsequent in time of origin to the rocks with which it is associated. Its mode of origin is not known, but it is probable that it was introduced by circulating water into the positions it now occupies. It is hardly likely that it is connected in any direct way with the great intrusions that forced themselves into the sedimentary beds and formed the widely prevailing gneisses of the Highlands.

Such a mode of origin would probably have resulted in many deposits, some of which would have been in the white limestone, which is much more common than the quartzite and shaly rocks associated with it. It seems more likely that the hematite was introduced before the advent of the igneous rocks, but from what source it was obtained is unknown.

Small quantities of the ore are also reported from a few localities at which the rocks associated with them are not the Franklin quartzites and conglomerates, but none of these localaties are of more than passing interest.

LOCALITIES.

Since the pre-Cambrian quartzites and shaly rocks in which the hematite deposits occur are in a few small scattered areas distributed irregularly over the western portion of the Highlands, the developments that have yielded the ore are also few and their locations widely scattered. Most of them, however, are in Sussex County.

DESCRIPTION OF INDIVIDUAL MINES.

There are two points near McAfee, in Vernon Township, Sussex County, at which hematite has been mined, but at neither place did the mining prove profitable (Fig. 3, page 60). The propositions were nothing more than large explorations. At both places the ore is associated with quartzites, conglomerates and the white Franklin limestone, but the exposures are not sufficiently abundant to warrant any definite statement as to the geological relationship of the ore.

(1) The Cedar Hill Mine.

The Cedar Hill, Smith's or the Ten Eyck mine is on the brow of the steep ridge of Franklin limestone just west of the village of McAfee. The rock west of the ore is white limestone, while that under it, i. e., on the southeast side, is a conglomerate of white quartzite pebbles in a dull reddish-green matrix, com

posed of chlorite and amorphous hematite. This occurs in a bed 40 or 50 feet thick which can be traced for a distance on its strike of about 500 feet. It stands on edge in a nearly vertical position and is exposed to a depth of 25 feet. It is apparently intercalated with the limestone.

The conglomerate is highly ferruginous, the hematite occurring largely in the interstices between the chlorite particles that constitute its principal mass, but it is too lean to be worked as an ore. Pyrite is present in considerable quantity through the rock, and portions of it contain crystalline grains of iron carbonate (siderite) about a half-inch in diameter. These are pearlgray on fresh fractures, but are rust-red on exposed surfaces. It is probable that the hematite may have been derived from these two minerals. The exploration was first opened about 1867. Several thousand tons were removed from two pits about 500 feet apart, but so far as known none was ever shipped. The mine was abandoned in 1872.

An analysis of a sample of the ore obtained when the mine was first opened gave:

References: N. J., 1868, p. 662; 1872, p. 20; 1873, p. 89; 1879, p. 90; Folio No. 161, U. S. Geol. S., 1908, pp. 21 and 23; Folio No. 2, Geologic Atlas of N. J., 1908, pp. 21 and 23.

(2) The Simpson Mine.

The Simpson mine is 2.5 miles northeast of Hamburg and about 1 mile southwest of McAfee, on the west side of the brow of the hill overlooking the Lehigh and Hudson River Railroad. (See Fig. 3.)

The geological conditions at this mine are not essentially different from those at the Cedar Hill mine. The hill is covered with glacial drift so that exposures are very few. Several openings, however, have been made which show the quartzite conglomerate lying in layers separated by shaly material. The