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132
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GEOLOGY OF NEW YORK CITY
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but
localized; developed in some force at Fort George, and here also
replaced in its hexagonal prismatic form by mica, quartz, and feldspar;
associated with green mica (muscovite),pink feldspar, and quartz; prism
and pyramidal planes in specimens from 190th Street and Amsterdam
Avenue; faintly blue, opaque, hexagonal prism from Manhattanville.
Biotite, the
magnesian iron mica, on the island invariably black, has been found in
crystals three inches long at 7th Avenue and 135th Street, and pockets
of rich crystal bunches at 56th Street, between 6th and 7th Avenues. It
is exhibited in black bundles of plates, curved and impressed. Large
masses at 136th to 141st Streets and 7th Avenue.
Bornite, erubescite,
peacock ore, copper and iron sulphide, found veining gneiss with
peacock stains, in contact with granite lenses; coloring, by
decomposition and oxidation, the mica, quartz, and feldspar a faint
grass green, asociated with azurite, which has been formed from it.
Bournonite, sulph-antimonide of lead and copper; reported by Hidden.
B.yssolite, green moss-like amphibole; reported.
Calcite, the
carbonate of calcium, is found in large rhom-bohedral crystallizations
as veins or seams in the dolomite, and recorded elsewhere, as in Harlem
Tunnel, in thin plates, and the hornblende schist or gneiss, at I22d
Street and Harlem Heights, holds interesting examples in cavities.
Calcite is not so common as might be anticipated. Found in the
dolomite, and seen with finely papillose sheaves of stilbite, scalenohedral, on gneiss at 45th Street and ist Avenue; elswhere in small crystals; with the ophiocalcite in West 58th Street.
Chabazite, hydrous
silicate of aluminum, calcium, and sodium; at 43d Street and East
River, at 45th Street and ist to 2d Avenues, rusty brown to gay-brown
rhombohedrons; 101st Street and 5th Avenue, brilliant red; 96th Street
and 4th Avenue, brown crystals on hornblende gneiss; 95th Street and
4th Avenue, chocolate brown; 44th Street and 2d Avenue, yellow.
Chalcopyrite, the
sulphide of copper and iron, is found with pyrite in the dolomite beds,
and infrequently in the gneiss. On oxidation it yields thin flakes or
films of malachite and azurite. An agent of the Kingsbury and Turner
Water Co. reported laminated massive chalcopyrite (much altered to
carbonate) from 108th Street and Columbus Avenue at a depth of 432
feet, associated with quartz.
Chert, drift.
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