94 GEOLOGY OF NEW YORK CITY
This
carbonate of lime has many small specks of serpentine diffused through
it, and forms a kind of 'verde antique,' which, when polished, makes
handsome specimens.
"
These early observers speak of the association of the serpentine with
hydrous anthophyllite, and this association points significantly to the
origin of the serpentine itself. This bed of serpentine is, in all
probability, an altered amphibole, or hornblende schist, and the '
porphyritic,' ' verde-antique,' eozoonal portions, the products of
such, are alterations produced under conditions of strain and
pressure, accompanied by aqueous infiltrations. I have not seen the
vein of anthophyllite alluded to above, but on visiting the locality
on 59th Street, where a ledge rises up in a mound-like prominence, I
found anthophyllite in masses, apparently recently blasted and removed
from their beds of place, with which was seen actin-olite largely
changed to serpentine. An examination of the hill showed a vertical
face where eozoon structure (ophio-calcite) was seen at a number of
points. It appeared in seam-like bands, expanding in some spots and
contracting at others, forming an irregular scattered prolongation of
parts, varying in grain from fine to coarse, the former accompanying an
apparent flexure or contraction of the original stratum. On the south
side of 50th Street, where the excavations were being made (mentioned
above), an exposure of the serpentine bed was accessible, where the
ophio-calcite was seen frequently presenting a seam-like appearance,
contracting to narrow bands and again developed in broader sections,
while sometimes it sporadically occupied nests in spots enclosed in the
surrounding rocks. Away from these parts the serpentine was fibrous or
micaceous."
Note.—The anthopyllite, serpentine, eozoonal sections referred
to above can be seen and examined by the teachers at any time in the
collection of New York Island Rocks and in the Mineral Cabinet of the
American Museum of Natural History.
