372 
GEOLOGY OF THE FIRST DISTRICT. 
“ The argillite is also employed to some extent in the construction and repair of roads ; il 
is, however, but a poor material for this purpose. The surface edges of the rock are gene¬ 
rally employed, and these of the variety containing the largest proportion of clay. The 
wheels soon reduce it to powder so fine that the wind drifts it when dry, and the water washes 
it away when wet. 
“ Anthracite is also disseminated in the grey wacke in masses from the size of a pin head 
to that of a pea, so as to give the rock quite a handsome appearance. This is strikingly the 
case at Walden, on the northwest bank of the Walkill. 
“ Beds of siliceous slate and lydian stone are embraced in this argillite. I have also seen 
graphic slate, but it is not abundant. In some places, the greywacke associated with the 
argillite forms a tolerably good building stone. It quarries very well, and works well under 
the hammer.”* 
Veins traverse the rocks of this group in various directions, but they are generally the 
same as those of the systems of joints. They are filled with quartz and carbonate of lime. 
The quartz is frequently crystallized, and the crystals adhere to the sides of the fissures, the 
remainder of the vein being vacant, or filled with carbonate of lime. Fibrous quartz and 
amorphous quartz, calcareous spar and satin spar, the former in fine crystals, and the latter 
in short fibres with a silky lustre, are often found in the veins. Small but brilliant crystals 
of pyrites are not uncommon in the veins in the grits and slates of this group. 
Wherever these rocks are quarried or exposed to view, either artificially or naturally, they 
are found to be upturned on their edges, or dip at a high angle, and are frequently curiously 
bent, contorted and broken, as if pitched together heterogeneously. The rocks are evidently 
sedimentary, and cannot have been formed in the position in which they now lie ; for, layers 
of sand and mud cannot lie in vertical laminae unsupported, and these rocks were evidently 
formed of sand and mud in parallel successive laminse and strata. The principal lines of 
fracture and of disturbance of the strata, with the effects, the phenomena connected with 
them, and the relative periods at which they occurred, will be discussed in a subsequent part 
of this volume. 
Sullivan County^ 
A small portion of this county is occupied by this group as the surface rock. The mass 
of the Shawangunk mountain is formed of rocks belonging to this group, except the small 
portion occupied by the Shawangunk grit. They are similar in character to those of Orange. 
Ulster and Greene Counties. 
The rocks of the Hudson»river group occupy the east and southeast parts of Ulster and 
Greene counties. The slates occur at Kingston point. They are also seen at Pine mountain. 
Third Annual Geological Report, 1839. 
