The narrow red band on the map represents the outcrop of the Ore sandstone approximately.
The Danville ore.
The Danville ore bed, so called from its large development at Danville in Montour county (where the Sand Vein is worthless) is usually separated from the Ore sandstone above by from 10′ to 30′ of purplish-red and calcareous shale. It is from 16″ to 18″ thick at Danville, where it has been most wrought, and shows a triple character, separated by thin slate seams. ‘These beds are spread through 6′ or 8′ of measures in Union county, are usually merely thin ferruginous limestone, but in places, as between Turtleville and New Berlin, the partings are thinner, and the different ore benches 4″ to 6″ thick are worked in the same gangways.
This is the principal bed along the south side of the Longstown ridge, and near Union Furnace at Turtleville the lowest of the three Danville beds is said to have yielded from 20″ to 3′ of ore.
The Middle olive shales, 150′±, intervene between the Danville ore rocks and the Iron sandstone.
The Iron Sandstone.
The latter rock is a hard dark red brittle sandstone, where typically developed, but it varies greatly. A series of sandstones and hard slates 60′ to 70′ thick occurring at this horizon is sometimes given the name; elsewhere a single bed 8′ to 10′ thick is called the Iron sandstone. It occasionally carries a little ore on top, known as the Block ore bed, and is itself frequently ferruginous enough to come within the term “iron ore.” But there is no demand for such ore as it can furnish now, and no ore was taken from this horizon at all during 1888.
The Lower Olive shales.
The lower olive shales, 500′ to 600′ thick, intervene between the Iron sandstone and the Medina sandstone, and it is largely these rocks which fill up the narrow valleys.
