Page:Report on the geology of the four counties, Union, Snyder, Mifflin and Juniata (IA reportongeologyo00dinv).pdf/97

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In Mifflin and Juniata county, very little in addition need be said to describe the Salina and Clinton formations. These rocks occupy wide belts through the Lewistown valley in Mifflin county, flanking Jack’s and Shade mountains; and the lower Clinton rocks also show in the Laurel Creek valley between Paddy and Long mountains.

The Salina rocks will be found close to the blue belt representing the Lower Helderberg limestone, because in this part of the district the dips are steeper and the breadth of the outcrop lessened. On the north side of the Lewistown valley, the Ore sandstone makes a high terrace on the south flank of Jack’s mountain until approaching the Juniata near Mt. Union, its dip decreases and throws the outcrop more to the south and towards the valley. From Union county to the Kishacoquillas, very little is known of the condition and thickness of this rock or the fossil-ore beds above and below it.

The outcrop of the “Sand Vein” is rather silicious in this part of the range; but the ore bed has never been regularly opened and therefore nothing is absolutely known of its character. Vast quantities of uncleared land belonging to the Logan Iron Company occupy this part of Jack’s mountain, in which explorations for ore have never been systematically carried on. The Ore sandstone is, however, quite massive and about 30′ thick, and dips about 60° south, so that these circumstances favor the occurrence of considerable bodies of soft ore here.

At Logan Gap, in Jack’s mountain, the Ore sandstone is about 20′ thick and dips 55° S. E.

The Danville ore beds have been found here, 3 in number, through a section of 15′, the upper bed being 15′ beneath the Ore sandstone. The largest is scarcely more than a foot thick, and the small pits have long since been closed. An analysis of the ore given in Report F, p 17, shows: