Davis Mine (Forbes Mine; Hendricks Mine), Salisbury Mining District, USAi

Regional Level Types
Davis Mine (Forbes Mine; Hendricks Mine)	Mine
Salisbury Mining District	Mining District (Abandoned)
USA	Country

At the “Davis” mine the country rock is entirely Stockbridge dolomite, furnishing in this respect an apparent exception to the general rule, which is that the ore bodies follow the boundary of Stockbridge dolomite with Hudson or Berkshire schist. The locality is, however, quite near the boundary of the two formations, and upon study it is found that a thin layer of the higher formation forms an impervious footwall to the ore body. The excavations at the mine were made upon the site of a local swampy area, which from our present knowledge of the structure was occasioned by local springs rising along fault fissures. The geological structure at the locality is set forth in figure 12.

The average dip of limestone at the mine is 25° to 30° southeast. Beneath the ore body is a distinct roll in the formation which brings it somewhat higher in the eastern portion of the pit. To the southeast, and similarly to the northwest, the dolomite rises from the foot of the ore body in a steep wall toward the surface. These walls are believed to represent planes of faulting. Their strike is approximately N. 50° E. (see Fig. 13). Covering the ore body was a thick layer of stratified drift and till which is now well exposed upon the north wall of the pit.

The lower layers of this material were hardpan - a mixture of clay with glaciated pebbles - having an approximately uniform southeast dip of 20°. Above the hardpan was till, which with the hardpan gave a total thickness of 75 feet in some places.

The base of the ore body is generally dolomite upon which is a thin layer (four to six feet) of hard black or grey slaty rock. The roll of the dolomite beneath the ore body was found to pitch 15° southwest. Toward the north wall of the pit the surface of the foot wall was warped in such a manner as to dip more nearly south. The fault walls bounding the pit upon the east and west have a dip of 700 or more to the northwest. From the massive dolomite of the steep western wall a copious spring of cold water now issues and was probably in part responsible for the swampy area once located above the site of the present pit.

In addition to this spring there was another southeast of the swampy area and across the Lincoln City brook, which brook now enters the mine in a fall over the fault plane at the west and flows through the mine. A clue to the explanation for the concentration of the large body of ore at this mine seems to be afforded by the small remnant of schist formed near the north wall, and by the fault walls which so largely bound the ore body. The ore body appears to represent a sunken block in which the superior Hudson schist, now largely represented by ore, has been inset within bounding walls of dolomitic limestone.