No. 200. J 
The grayband, which is a distinct stratum of four or five feet thick*- 
siess, at Rochester, is represented by a few inches of gray marl at Lock- 
port, and is ten feet thick on the Niagara river, where it passes imper- 
ceptibly into the red rock beneath. Small particles of pyritous copper, 
and green carbonate of copper, occur in the gray band at Lewiston. — - 
Iron pyrites occurs in the red sandstone at Holley, Orleans county. 
The points at which this formation can be most advantageously exa- 
mined, are along the Genesee river, below Rochester, at Medina, Or- 
leans county, and along the Niagara river, near Lewiston. 
SECTION II. 
Argillac&ms and Calcareous Shales of the Genesee and JYiagara rivers. 
The marl and sandstone just described, are succeeded by a series of 
argillaceous and calcareous shales, with interposed beds of limestone. — 
The lower portions are argillaceous, with thick beds of siliceous lime- 
stone. The upper portions are calcareous, with seams, or thin strata, of 
blue limestone, the whole changing, above, into an impure limestone.^ 
Resting on the sandstone at Rochester, we have a green shale, about 
twenty feet thick, the upper portions alternating with thin strata of sili- 
ceous limestone. Above the shale, we have a stratum of argillaceous 
iron ore, about one foot thick. Above this, we have calcareous and si- 
liceous strata, of about fourteen feet thickness, separated throughout by 
thin seams of shale. Upon this rock, we have twenty-four feet of green 
shale, similar to that below, and above this, eighteen feet of silico-cal- 
careous strata, separated by seams of shale. The last is not so siliceous 
as that above the lower green shale. The green shales, both lower and 
upper, consist of irregular laminae, very fissile and tender, and on expo- 
sure, readily dissolving into a tenaceous clay. The lower stratum is 
commonly of a bright green or blueish green colour, but changes on ex- 
posure. The upper shale is of a less vivid colour, often inclining to a 
grayish green. The strata of siliceous limestone interposed between 
the two shales, are coarse grained, and of a harsh texture, breaking into 
irregular blocks. Some of the more siliceous strata are compact and 
fine grained, and some portions, in thin strata or masses, have become 
cherty or chalcedonic. We often find specimens of pure chalcedony 
*The lower shale and siliceous limestone of this series, have been called the " Ferriferous 
rocks," by Prof. Eaton. This term may be applicable to these rocks, in some places, but is 
peculiarly inappropriate for the whole series, as iron is no where found in these rocks between 
the Genesee and Niagara rivers. The term " Sandrock," cannot, with propriety, be applied to 
any portion of these rocks, except a few feet of the lower bed of siliceous limestone at Rocties- 
ter. Both the Ferriferous slate," and the "Ferriferous sandrock," are distinctly repeated above 
the iron stratum, in a second green shale, and a second bed of siliceous limestone. The upper 
green shale and upper limestone are easily mistaken for the series below, indeed the digtinction 
18 merely nominal, depending on the accidental presence of iron ore. 
[Assem No.200.] 34 
