Page:Report on the geology of the four counties, Union, Snyder, Mifflin and Juniata (IA reportongeologyo00dinv).pdf/332

304 F³. feet deep, extending from the top of the ridge and separated from each other by a strip of untouched ground into which entries were being extended underground. The stone crops well to the surface, where the southeast dip is not over 20°, but which stiffens towards the bottom of the cuts to one of 40°. A drift has been run northwards from the washer at the railroad for 300′ at a lower level than the bottom of either open quarry. A main gangway is driven from the end of the drift in a westward direction a little south of and below the open cuts and which serves through stopes driven up to the bottom of the open cuts to load the material quarried and convey it to the washers. All the blasting was being done in these two open cuts, and the broken stone was thrown down through shoots directly into cars standing in the main gangway. All of the stone exposed in these open quarries has a buff color and rusty appearance, but there does not seem to be any inherent blemish in the rock as after crushing and washing it it appears perfectly white and clear.

The stone sand beds here show a very distinct set of cleavage planes which dip towards the northwest at right angles to their stratification, so that one is very apt to be confused by them and to alternate true dip with cleavage. In addition to both dip and cleavage there are immense joints or seams called “heading courses” by the quarrymen, which occur along the length of the beds sometimes every 10′, sometimes 50′ to 100′ apart.

The main drift is not driven directly across the strike of the measures, and with sufficient grade to permit the loaded half-ton cars to deliver themselves by gravity from the working faces, to which they are pushed back when emptied almost from the entrance. From the drift the tunnel passes through irregularly bedded and very hard sandstone, having a variable dip, but probably basining before the workable or lower portion of the bed is reached in the rear portion of the workings. This bed is about 125′ thick. It is overlaid by a hard rim of cherty sand rock, which really creates the crest of the ridge and is underlaid by a “soapstone” footwall to which the gangways are carried.