West 56th and 57th Streets, near 6th and 7th Avenues. Found streaking the hornblende rocks.
Essonite, light colored garnet, attractively set in white feldspar and glistening silvery mica, at Fort George.
Fibrolite, silicate of aluminum, in white-gray fibres at Fort George, Washington Heights, 52d Street and Madison Avenue.
Fluorite, fluoride
of calcium noted by Hidden, " in yellow and blue cubes 1-4 inch in
diameter, on gneiss at Hell Gate." H. S. Williams found a large (six
inches by three) greenish block of fluorite, with rusty brown
separations, between 53d and 54th Streets on Broadway in the Subway.
This region has been prolific of mineral treasures. This fluorite is
exhibited in collection of New York Mineralogical Club. Rare.
Fluocerite, a fluoride of rare bases, cerium, didymium, lanthanum, yttrium, erbium; very rare; one specimen reported by Hidden.
Galenite, sulphide
of lead, cubic crystals from 43d Street and East River, from Aqueduct
Shaft No. 27; crystals on stilbite (F. A. Camp) from Harlem at Convent
Avenue; unusual, also with chabazite, 92d and 96th Streets, and 4th
Avenue.
Garnet, a
variable silicate containing, on Manhattan Island, usually aluminum,
iron, magnesium, and calcium. Garnets are plentiful throughout the
island rock, dense concretions of them (the so-called seed garnet) of a
pale red color, associated with apatite, having been taken from a vein
in 83d Street and Amsterdam Avenue, while inserted over the faces of
orthoclase in a cross-cut granite vein at 65th Street garnets (Fig. 33)
with modified dodecahedral faces of deep brown were found in 1888. Dr.
Kunz has an enormous specimen, weighing nine pounds ten ounces, of a
dull brown, now exhibited in the collection of the New York
Mineralogical Club at the Museum of Natural History. In many
localties, especially in granite seams, this familiar mineral is
encountered.
Mr.
Chamberlin remarks that from Lenox Avenue and 119th Street " eastward
and northward to Mount Morris Park, pockets and veins of garnets abound
in greater number than in any portion of the city or county. The rocky
heights of the Park are thickly studded with weathered crystals. The
find of good cabinet specimens is, unfortunately, quite limited."
Mr. Niven has uncovered some large distorted crystals on the Speedway.
In the Chamberlin collection is a gem-like crystal of garnet, dense in places, penetrated by a crystal (prism) of black tourma-
