172 DR. THOMAS STERRY HUNT ON THE 
§ 19. The serpentine of Brinton’s quarry, near Westchester, Pennsylvania, is distinctly 
bedded, granular, and often finely laminated, with disseminated scales of a micaceous 
mineral, giving it a gneissoid structure and aspect. A black schistose hornblendic rock, 
with red garnet, is said to have been found in an excavation adjoining the serpentine, and 
fragments gathered in the vicinity showed thin interlaminations of black horn- 
blende with greenish serpentine. The dip of the strata, of which several hundred feet are 
here exposed, is to the northwest at a high angle, approaching the vertical. They are 
traversed, nearly at right angles, by a vertical granitic vein, which has been traced for 
many hundred feet in a northwest course. This vein, which is generally from three to 
six feet in breadth, is white in color, and in parts may be described as a fine-grained binary 
granite, the feldspar of which is superficially kaolinized. In other parts, it becomes very 
coarse-grained, presenting large cleavage-forms of orthoclase. A banded or zoned structure, 
parallel to the well-defined walls, is observed in some parts, and in one case a lenticular 
mass of white vitreous quartz occupies the centre. This vein-stone, which carries black 
tourmaline, and is said to have afforded beryl, has all the characters of the ordinary en- 
dogenous granitic veins found in the gneissic rocks of the Appalchians, which veins I 
have elsewhere described in detail. * 
§ 20. The rocks in the vicinity of the serpentine near Westchester are, as already said, 
deeply decayed, but wherever seen in the cuttings are found to be mica-schist and mica- 
ceous gneiss. Such rocks, with a northwest dip, appear to underlie, at no great distance, 
the mass of serpentine exposed at Stroud’s mill. Similar rocks are also found on the rail- 
road between Westchester and Media, where they are exposed in a cutting near the latter 
station, about a mile from which is found a great outcrop of distinctly stratified serpentine, 
resembling that of Brinton’s quarry, and with a steep northwest dip. It includes an inter- 
stratified mass, about twenty feet thick, of a fine-grained reddish gneissoid rock, approach- 
ing leptynite or granulite in character, divided into distinct beds generally from four to 
eight inches in thickness, between which are sometimes found layers of a few inches, of 
a soft serpentine, and, in one case, of a broadly foliated green chloritic mineral. Consider- 
able differences in texture and aspect were observed between the serpentine-beds below 
and those above this quartzo-feldspathic mass, which is indigenous, and not to be con- 
founded with the endogenous transversal mass described at Brinton’s quarry. 
§ 21. Serpentine-rocks also occur on Manhattan Island, in the city of New York, 
where they are still exposed between Fifty-seventh and Kixtieth streets, west of Tenth 
avenue, and are directly interstratified in gneissic and micaceous rocks, which may either 
belong to the older gneiss series of the Highlands, or to a newer group. Associated with 
the massive serpentine of this locality are found small quantities of a granular ophicalcite, 
and near it is a mass of anthophyllite-rock. This locality was long since described by Dr. 
Gale, when the rocks were more fully exposed than at present. + 
§ 22. Serpentine-masses are also found in the vicinityof the last, on Staten Island, and 
at Hoboken, in both of which localities the encasing gneisses, seen in New York city, are 
wanting, and the serpentine appears along the eastern margin of the triassic belt of the 
region. The serpentine of Staten Island is of much interest, as it presents many fea- 

* Amer. Jour. Science (3) i. 182-187, and Chem. and Geol. Essays, pp. 192-200, 
+ Mather, Geology of the Southern District of New York, p. 461. 
