GENESEE COUNTY. 
465 
northern point that I have found it, in the county. At this place some thirty or forty tons were 
quarried; but the masses being small, and about eight feet below the surface, requiring the 
removal of all the superincumbent earth and stone, the work proved unprofitable, and was 
abandoned. 
In the vicinity of this quarry, and for some distance west, there are sufficient indications 
of gypsum in the peculiar irregularity of the surface, which is raised into little mounds, 
giving it the appearance of heaps of earth deposited on the level soil. The thin bluish or drab 
limestone is also found near the surface, and often ploughed up in the fields. 
In the north part of Leroy, plaster is obtained in large quantities, on lots 118, 144 and 132. 
The quarries in the first are of white gypsum, free from seams and intermixture of clay ; it is 
covered with a bluish kind of limestone with shaly seams, and which separates into laminae 
one-fourth or one-half an inch thick. In the others, the gypsum is clay-colored, with seams of 
clay; this, when exposed, crumbles rapidly. The rock above is a drab limestone, resembling in 
general appearance the hydraulic limestone. In this I found some few fossil shells of a spe¬ 
cies of Avicula. Some parts of the rock are filled with small round pores, the size of a mustard 
seed ; such are also seen in the soft limestone, a few feet below the hydraulic or drab lime¬ 
stone. The masses of gypsum are all more or less spherical; the surrounding rocks being 
raised in the centre, presents a fractured convex surface, dipping on every side. 
The quarries last mentioned, belong to Messrs. Bannister, Collins and Clifford ; the white 
gypsum to Mr. Hughes and Mr. Cash. The plaster is sold at the bed for fifty cents, and 
when ground, from three dollars to three dollars and fifty cents per ton. The different beds 
in this county furnish about three thousand tons annually. 
The formation described, belongs apparantly to the second or middle series of gypsum beds ; 
the upper, like that at Seneca-falls and Vienna, is not seen, neither have I been able to find 
the lower series ; but although similar in general character, it would appear that the white 
gypsum above described, which is half a mile north from the others, must be at a different 
elevation, as well from its position as from its associated rocks. The general direction of the 
masses is N. W. and S. E., as appears both from the beds here, and from their reappearance 
in the western part of Elba. 
The alluvial excavation along the valley of Black and Bigelow creeks, has either removed 
the gypsum, or covered it so deeply with drift that it is not reached in ordinary excavations ; 
but unless so removed, the whole distance across the country is probably underlaid by it, 
though its depth may be too great for profitable exploration. 
The gypsum is succeeded by various colored marls, mostly bluish, greenish and drab or 
ash-colored ; some hard and very calcareous ; others soft, crumbling, and forming a tenacious 
clay. 
The drab limestone, or hydraulic limestone, is the next succeeding mass. The essential cha¬ 
racters of this rock have already been described ; its thickness is variable, and also the pro¬ 
portion of sand, clay and carbonate of lime. Its connexion with the Onondaga limestone 
above, is seen to advantage at the falls on Allen’s creek, two miles north of Leroy; and also 
[Geol. 4th Dist.] 59 
