THE MINERALOGICAL LOCALITIES IN AND AROUND NEW YORK CITY, AND THE MINERALS OCCURRING THEREIN.
[Footnote: Continued from SUPPLEMENTS 244 and 246.]
By NELSON H. DABTON.
PART III.
Hoboken.--The locality represented here is where the same serpentine that we met on Staten Island crops out, and is known as Castle Hill. It is a prominent object in view when on the Hudson River, lying on Castle Point just above the Stevens Institute and about a mile north of the ferry from Barclay or Christopher Street, New York city. Upon it is the Stevens estate, etc., which is ordinarily inaccessible, but below this and along the river walk, commencing at Fifth Street and to Twelfth, there is an almost uninterrupted outcrop from two to thirty feet in thickness and plentifully interspersed with the veins of the minerals of the locality, which are very similar to those of Staten Island; the serpentine, however, presenting quite a different appearance, being of a denser and more homogeneous structure and color, and not so brittle or light colored as that of Staten Island, but of a pure green color. The veins of minerals are about a half an inch to--in the case of druses of magnesite, which penetrate the rock in all proportions and directions--even six inches in thickness. They lie generally in a perpendicular position, but are frequently bent and contorted in every direction. They are the more abundant where the rock is soft, as veins, but included minerals are more plentiful in the harder rock. There is hardly any one point on the outcrop that may be said to be favored in abundance, but the veins of the brucites, dolomite, and magnesites are scattered at regular and short intervals, except perhaps the last, which is most plentiful at the north end of the walk.
Magnesite.--This mineral, of which we obtained some fine specimens on Staten Island, occurs extremely plentifully here, constituting five or six per cent. of a large proportion of the rock, and in every imaginable condition, from a smooth, even, dark colored mass apparently devoid of crystalline form, to druses of very small but beautiful crystals, which are obtained by selecting a vein with an opening say from a quarter to a half-inch between it and one or, if possible, both points of its contact with the inclosing rock, and cutting away the massive magnesite and rock around it, when fine druses and masses or geodes may be generally found and carefully cut out. The crystals are generally less than a quarter of an inch long, and the selection of a cabinet specimen should be based more upon their form of aggregation that the size of the crystals. Nearly all the veins hold more or less of these masses through their total extent, but many have been removed, and consequently a careful search over the veins for the above indications, of which there are still plenty undeveloped or but partly so, would well repay an hour or more of cutting into, by the specimens obtained. Patience is an excellent and very necessary virtue in searching for pockets of minerals, and is even more necessary here among the multitudinous barren veins. One hint I might add, which is of final importance, and the ignorance of which has so far preserved this old locality from exhaustion, is that every specimen of this kind in the serpentine, of any great uniqueness, is to be found within five feet from the upper or surface end of the vein, which in this locality is inaccessible in the more favored parts without a ladder or similar arrangement upon which one may work to reach them. Here the veins will be found to be very far disintegrated and cavernous, thus possessing the requisite conditions of occurrence (this is also true of Staten Island, but there more or less inaccessible) for this mineral and similar ones that occur in geodes or drused incrustations, while it is just vice versa for those occurring in closely packed veins, as brucite, soapstone, asbestos, etc., where they occur in finer specimens, where they are the more compact, which is deep underground. This is also partly true of the zeolites and granular limestone species with included minerals. I do not think there is any rule, at least I have not observed it in an extended mineralogical experience; but if they favor any part, it is undoubtedly the top, as in the granular limestone and granite; however, they generally fall subordinate to the first principle, as they more frequently, in this formation, with the exception of chromic iron, occur not in the serpentine but in the veins therein contained; for instance, crystals of dolomite are found deeper in the rock as they occur in the denser soapstone, which becomes so at a more or less considerable depth, with spinel, zircon, etc., of the granular limestone. They occur generally in pockets within five feat from the surface, but they can hardly be called included minerals, as they are rather, as their mention suggests, pockets, and adjacent or in contact with the intruded granite or metamorphosed rock joining the formation at this point. This is seemingly at variance when we consider datholite, but when we do find it in pockets a hundred and fifty feet below the surface, in the Weehawken tunnel, it is not in the trap, but on the surface of what was a cleft or empty vein, since filled up with chlorite extending from the surface down, while natrolite, etc., by the trap having clefts of such variable and often great depth, allowed the solution of the portion thus contributed that infiltered from the surface easy access to the beds in which they lie, the mode of access being since filled with densely packed calcite, which was present in over-abundance. This is not applicable to serpentine, as the clefts are never of any great depth, and the five feet before mentioned are a proportionately great depth from the surface. As I mentioned in commencing this paper (Part I), every part of the success of a trip lies in knowing where to find the minerals sought; and by close observation of these relations much more direction may be obtained than by my trying to describe the exact point in a locality where I have obtained them or seen them. There is much more satisfaction in finding rich pockets independently of direction, and by close observance of indications rather than chance, or by having them pointed out; for the one that reads this, and goes ahead of you to the spot, and either destroys the remainder by promiscuous cuttings, or carries them off in bulk, as there are many who go to a locality, and what they cannot carry off they destroy, give you a disappointment in finding nothing; consequently, I have considered that this digression from our subject in detail was pardonable, that one may be independent of the stated parts of the locality, and not too confidently rely on them, as I am sometimes disappointed myself in localities and pockets that I discover in spare time by finding that some one has been there between times, and carried off the remainder. The characteristics of magnesite I have detailed under that head under Pavilion Hill, Staten Island; but it may be well to repeat them briefly here. Form as above described, from a white to darker dirty color. Specific gravity, 2.8-3; hardness, about 3.5. Before the blowpipe it is infusible, and not reduced to quicklime, which distinguishes it from dolomite, which it frequently resembles in the latter's massive form, common here in veins. It dissolves in acid readily with but little effervescence, which little, however, distinguishes it from brucite, which it sometimes resembles and which has a much lower-specific gravity when pure.
Dolomite.--This mineral has been very common in this locality. It differs, perhaps, as I have before explained, from magnesite in containing lime besides magnesia, and from calc spar by the vice versa. Much of the magnesite in this serpentine contains more or less lime, and is consequently in places almost pure dolomite, although crystals are seldom to be found in this outcrop, it all occurring as veins about a half-inch thick and resembling somewhat the gurhofite of Staten Island, only that it is softer and less homogeneous in appearance. Its color is slightly tinged green, and specimens of it are not peculiarly unique, but perhaps worth removing. Its characteristics are: first, its burning to quicklime before the blowpipe, distinguishing it from pure magnesite; second, its slow effervescence in acids. Besides these, its specific gravity is 2.8, hardness, 8.5; from calcspar it cannot be distinguished except by chemical analysis, as the two species blend almost completely with every intermediate stage of composition into either calc spar, or, what occurs in this locality, aragonite, similar in composition to it, or dolomite. The color of the last, however, is generally darker, and it cleaves less readily into its crystalline form, which is similar to calc spar, and of which it is harder, 3.5 to 3 of calc spar.
Aragonite.--This mineral, identical in composition with calc spar, but whose crystalline form is entirely different, occurs in this locality in veins hardly recognizable from the magnesite or dolomite, and running into dolomite. It is not abundant, and the veins are limited in extent; the only distinguishment it has from the dolomite, practically, is its fibrous structure, the fibers being brittle and very coarse. If examined with a powerful glass, they will be seen to be made up of modified long prisms. The specific gravity is over 2.9, hardness about 4, unless much weathered, when it becomes apparently less. There are some small veins at the north end of the walk, and in them excellent forms may be found by cutting into the veins.
Brucite.--This mineral occurs here in fair abundance, it being one of the principal localities for it in the United States, and where formerly extremely unique specimens were to be obtained. It has been pretty well exhausted, however, and the fine specimens are only to be obtained by digging into the veins of it in the rock, which are quite abundant on the south end of the walk, and, as I before noted, as deep as possible from the top of the veins, as it is a closely packed mineral not occurring in geodes, druses, etc. Two forms of it occur; the one, nemalite, is in fibers of a white to brown color resembling asbestos, but the fibers are brittle, and hardly as fine as a typical asbestos. It is packed in masses resembling the brucite, from which it only differs in breaking into fibers instead of plates, as I have explained in my description of that species (see Part II). They are both readily soluble in acids, with effervescence, and infusible but crumble to powder before the blowpipe, or at least become brittle; when rubbed in mass with a piece of iron, they phosphoresce with a yellow light; specific gravity, 2.4, hardness, 1.5 to 2. Its ready solubility in acids without effervescence at once distinguishes it from any mineral that it may resemble. The specimens of nemalite may be more readily obtained than the brucite but fine specimens of both may be obtained after finding a vein of it, by cutting away the rock, which is not hard to do, as it is in layers and masses packed together, and which maybe wedged out in large masses at a time with the cold chisel and hammer, perhaps at the rate of three or four cubic feet an hour for the first hour, and in rapidly decreasing rate as progress is made toward the unweathered rock and untouched brucite, etc.
Serpentine.--Fair specimens of this may be obtained of a dark oil green color, but not translucent or peculiarly perfect forms. The variety known as marmolite, which splits into thin leaves, is plentiful and often well worth removing.
Chromic Iron.--Crystals of this are included in the denser rock in great abundance; they are very small, seldom over a few lines in diameter, of an iron black color, of a regular octahedral form; sometimes large crystals may be found in place or in the disintegrated loose rock. I have seen them a half inch in diameter, and a half dozen in a small mass, thus forming an excellent cabinet specimen. By finding out by observation where they are the thickest in the rock, and cutting in at this point, more or less fine crystals may be obtained. This is readily found where they are so very abundant, near the equidistant points of the walk, that no difficulty should be encountered in so doing. These characteristics are interesting, and if large specimens cannot be obtained, any quantity of the small crystals may be split out, and, as a group, used for a representative at least. Before the blowpipe it is infusible, but if powdered, it slowly dissolves in the molten borax bead and yields a beautiful green globule. The specific gravity, which is generally unattainable, is about 4.5, and hardness 5 to 6. Its powder or small fragments are attracted by the magnet. A few small veins of this mineral are also to be found horizontally in the rock, and small masses may be obtained. They are very rare, however. I have seen numerous agates from this locality, but have not found them there myself. They may be looked for in the loose earth over the outcrop, or along the wall of the river. Our next locality is Paterson, N. J., or rather in a trip first to West Paterson by the D.L. & W. Railroad, Boonton branch, then back to Paterson proper, which is but a short distance, and then home by the Erie road, or, if an excursion ticket has been bought, on the D.L. & W, back from West Paterson. Garret Rock holds the minerals of Paterson, and although they are few in number, are very unique. The first is phrenite. This beautiful mineral occurs in geodes, or veins of them, near the surface of the basalt, which is the characteristic formation here, and lies on the red sandstone.
These veins are but two or three feet from the surface, and the ones from which the fine specimens are to be and have been obtained are exposed by the railroad cutting about a thousand feet north of the station at West Paterson, and on the west side of the rails. Near or below the beds is a small pile of debris, prominent by being the only one in the vicinity near the rails. In this loose rock and the veins which are by this description readily found and identified, they are about three inches in thickness, and in some places widen out into pockets even a foot in diameter They look like seams of a dark earth, with blotches of white or green matter where they are weathered, but are fresher in appearance inside. The rock, in the immediate vicinity of the veins, is soft, and may be readily broken out with the hammer of, if possible, a pick bar, and thus some of these geode cavities broken into, and much finer specimens obtained than in the vein proper. Considerable occurs scattered about in the before-mentioned pile of loose rock and debris, and if one does not prize it sufficiently to cut into the rock, taking the chances of lucky find, plenty may be obtained thus; but as it has been pretty thoroughly picked over where loose, it is much more satisfactory to obtain the fine specimens in place in the rock. When the bed for the railroad was being cut here, many fine specimens were obtained by those in the vicinity, and the natives of the place have it in abundance, and it may be obtained from many of them for a trifle, if one is not inclined to work it out. The mineral itself occurs in masses in the vein of a white, greenish white, or more or less dark green color. Sometimes yellowish crystals of it occur plentifully in short thick prisms, but the common form is that of round coralloid bunches, having a radiated structure within. Sometimes it is in masses made up of a structure resembling the leaves of a book slightly opened, and in nearly every shape and size. Crystals of the various forms may be well secured, and also the different colors from the deep green to the blue white, always remembering that true, perfect crystals are of more value than masses or attempted forms. The specific gravity is 2.8 to 2.9, hardness nearly 7 before the blowpipe; it readily fuses after intumescing; it dissolves in hot acid without gelatinizing, leaving a flaky residue.
Datholite.--This mineral is very abundant as inferior specimens, and frequently very fine ones may be obtained. They occur all around Garret Rock at the juncture of the basalt and red sandstone, in pockets, and as heavy druses. They are most abundant near the rock cuttings between West Paterson and Paterson, and may be cut out by patient labor. This is a long known and somewhat noted locality for datholite, and no difficulty need be experienced in obtaining plenty of fair specimens. Near them is the red sandstone, lying under the basalt, and baked to a scoriaceous cinder. Upon this is a layer of datholite in the form of a crystalline plate, and over or above this, either in the basalt or hanging down into cavities in the sandstone, are the crystals or geodes of datholite. Old spots are generally exhausted, and consequently every new comer has to hunt up new pockets, but as this is readily done, I will not expend further comment on the matter. The datholite, as in other localities, consists of groups of small colorless crystals. Hardness, about 5; specific gravity, 3. Before the blowpipe it intumesces and melts to a glassy globule coloring the flame green, and forms a jelly when boiled with the acids.
Pectolite--This mineral is also quite abundant in places, the greater part occurring with or near the phrenite before mentioned, in small masses generally more or less weathered, but in very fair specimens, which are about an inch in thickness. It is readily recognized by its peculiar appearance, which, I may again repeat, is in fibrous masses, these fibers being set together in radiated forms, and are quite tough and flexible, of a white color, and readily fused to a globule before the blowpipe.
Feldspar.--This mineral occurs strewn over the hill from place to place, and is peculiarly characterized by its lively flesh red color, quite different from the dull yellowish gray of that from Staten Island or Bergen Hill. Fine crystals of it are rather rare, but beautiful specimens of broken groups may be obtained in loose debris around the hill and in its center. I have not been able to locate the vein or veins from which it has come, but persistent search will probably reveal it, or it may be stumbled upon by accident. Some of the residents of the vicinity have some fine specimens, and it is possible that they can direct to a plentiful locality. However, some specimens are well worth a thorough search, and possess considerable value as mineralogieal specimens. The specific gravity of the mineral is 2.6, and it has a hardness of 6 before the blowpipe. It is with difficulty fused to a globule, more or less transparent. It occurs undoubtedly in veins in the basalt and near the surface of the outcrop As this locality has never before been mentioned as affording this species, it is fresh to the amateur and other mineralogists, and there need be no difficulty in obtaining some fine specimens. Its brilliant color distinguishes it from other minerals of the locality.
It is possible that some of the other zeolites as mentioned under Bergen Hill occur here, but I have not been able to find them. The reason may be that the rock is but little cut into, and consequently no new unaltered veins are exposed.
COPPER MINES, ARLINGTON, N. J.--A short distance north of this station, on the New York and Greenwood Lake Railroad, and about nine miles from Jersey City, is one of the cuttings into the deposits of copper which permeate many portions of the red sandstone of this and the allied districts in Connecticut and Massachusetts, and which have been so extensively worked further south at Somerville and New Brunswick, etc. There are quite a variety of copper minerals occurring in these mines, and as they differ but little in anything but abundance, I will describe this, the one nearest to New York City, as I promised in commencing these papers. The locality of this mine may be readily found, as it is near the old turnpike from Jersey City, along which the water-pipes or aqueduct, are laid. By taking the road directly opposite to the station at Arlington, walking north to its end, which is a short distance, then turning to the left along the road, there crossing and turning north up the next road joining this, until the turnpike is reached; this is then followed east for about a quarter-mile, passing occasional heaps in the road of green earth, until the head of a descent is reached, when we turn off into the field to the left, and there find the mine near the heaps of greenish rocks and ore scattered about, a distance from the station of about a mile and a half through a pleasing country. The entrance to the mine is to the right of the bank of white earth on the edge of, and in the east side of the hill; it is a tunnel more or less caved in, running in under the heaps of rock for some distance. It will not be necessary, even if it were safe, to venture into the mine, but all the specimens mentioned below may be obtained from the heaps of ore and rock outside, and in the outcrops in the east side of the hill, a little north of the mouth of the tunnel to the mine. The hammer and cold chisel will be necessary, and about three hours should be allowed to stay, taking the noon train from New York there, and the 5.09 P.M. train in return, or the 6.30 A.M. train from the city, and the 1.57 P.M. in return. This will give ample opportunity for the selection of specimens, and, if time is left, to visit the water works, etc.
Green Malachite.--This is the prominent mineral of the locality, and is conspicuous by its rich green color on all the rocks and in the outcrops. Fine specimens of it form excellent cabinet specimens. It should be in masses of good size, with a silky, divergent, fibrous structure, quite hard, and of a pure oil green color, for this purpose. Drused crystals of it are also very beautiful and abundant, but very minute. As the greater part of it is but a sixteenth or eighth of an inch in thickness, it may require some searching to secure large masses a quarter to a half-inch in thickness, but there was considerable, both in the rock, debris, and outcrop, remaining the last visit I made to the place a few months ago. The mineral is so characterized by its color and solubility in acid that a detailed description of it is unnecessary to serve to distinguish it. Its specific gravity is 4, and hardness about 4. It decrepitates before the blowpipe, but when fused with some borax in a small hollow on a piece of wood charcoal, gives a globule of copper. It readily dissolves in acids, with effervescence, as it is a carbonate of copper.
Red Oxide of Copper--This rather rare mineral is found in small quantities in this mine, or near it, in the debris or outcrop. Perfect crystals, which are of a dodecahedral or octahedral form, are fairly abundant. They are difficult to distinguish, as they are generally coated, or soiled at least, with malachite. The color proper is of a brownish red, and the hardness about 4, although sometimes, it is earthy, with an apparent hardness not over 2. The crystals are generally about a quarter of an inch to a half of an inch in diameter, and found inside the masses of malachite. When these are broken open, the red copper oxide is readily distinguished, and may be separated or brought into relief by carefully trimming away the malachite surrounding it as its gravity (6) is much greater than malachite. When a piece of the last is found which has a high gravity, it may be suspected and broken into, as this species is much more valuable and rarer than the malachite which is so abundant. It dissolves in acids like malachite, but without effervescence, if it be freed from that mineral, and acts the same before the blowpipe. Sometimes it may be found as an earthy substance, but is difficult to distinguish from the red sandstone accompanyit, which both varieties resemble, but which, not being soluble in the acids, find having the blowpipe reactions, is thus characterized. This red oxide of copper does not form a particularly showy cabinet specimen, but its rarity and value fully compensate for a search after it. I have found considerable of it here, and seen some little of it in place remaining.
Chrysorolla.--This mineral, very abundant in this locality, resembles malachite, but has a much bluer, lighter color, without the fibrous structure so often present in malachite, and seldom in masses, it only occurring as light druses and incrustations, some of which are very beautiful, and make very fine cabinet specimens. Its hardness is less than that of the other species, being under 3, and a specific gravity of only 2, but as it frequently occurs mixed with them, is difficult to distinguish. It does not dissolve in nitric acid, although that takes the characteristic green color of a solution of nitrate of copper, as from malachite or red oxide. This species is found all over this locality, and a fine drused mass of it will form an excellent memento of the trip.
Copper Glance.--This mineral is quite abundant in places here, but fine crystals, even small, as it all is, are rare. That which I have seen has been embedded in the loose rock above the mine, about a quarter inch in diameter, and more or less disguised by a green coating of chrysocolla. The color of the mineral itself is a glistening grayish lead color, resembling chromite somewhat in appearance, but the crystals of an entirely different shape, being highly modified or indistinct rhombic prisms. The specific gravity is over 5, and the hardness 4. Before the blowpipe on a piece of wood charcoal it gives off fumes of sulphur, fuses, boils, and finally leaves a globule of copper. In nitric acid it dissolves, but the sulphur in combination with it separates as a white powder. A steel knife blade placed in this solution receives a coating of copper known by its red color.
Erubescite--This mineral occurs massive in the rock here with the other copper minerals, and is of a yellowish red color, more or less tarnished to a light brown on its surface, Before the blowpipe on charcoal it fuses, burns, and affords a globule of copper and iron, which is attracted by the magnet. Its specific gravity is 5, hardness 3. It resembles somewhat the red oxide, but the low gravity, inferior hardness, lighter color, and blowpipe reaction distinguish it. These are the only copper minerals likely to be found at this mine, and the following table and note will show their characteristics:
Name. Speci- Hardness Action of Action of Color. Form.
fic Blowpipe Heat. Hot Nitric
Gravity. Acid.
Mala- From 4 From 3 Decrepitates, Dissolves Pure Oil Fibrous,
chite to 4.5 to 4 but fuses with with Green. massive,
borax to a effer- or in-
green bead. vescence crusting.
Red 6 From 3.5 On charcoal Dissolves A deep Modified
Oxide to 4 yields a without brownish crystals.
globule of effer- red.
copper. vescence
Chryso- From 2 From 2 Infusible. Partly Bright Incrus-
colla to 2.3 to 3 soluble bluish tations.
green.
Copper 5 From 2.5 Fumes of Copper Grayish Modified
Glance to 3 sulphur and a soluble, Lead. rhombic
globule of sulphur prisms.
copper deposits
Erube- 5 From 3 Fumes of Partly Yellowish Massive.
scite to 3.5 sulphur and soluble red or
magnetic tarnished.
globule.
Malachite is characterized by its color from Copper Glance and Red Oxide and Erubescite, and from Chrysocolla by the action of the acid, the fibrous structure and blowpipe reaction, gravity, and hardness.
Red Oxide is distinguished from Erubescite, which it alone resembles, by its darker color, higher specific gravity, and yielding a globule of pure copper.
Chrysocolla is characterized by its low specific gravity, light color, lack of fibrous structure, blowpipe reactions, and the acid.
Copper Glance is distinguished by its color, fumes of sulphur, and globule of copper.
Erubescite is distinguished from Red Oxide, which it alone resembles, by its lighter color, great solubility when pure, and yielding a magnetic globule before the blowpipe in the hollow of a piece of wood charcoal, which is used instead of platinum wire in this investigation.