Page:The Journal of geology (IA journalofgeology11893univ).pdf/294

widening to a maximum, where exposed, of three and a half feet. On the west slope of the knoll the ore bed is not seen at all, the only trace of it being an occasional black stain or dendrites in the limestone along the line where it should outcrop if it extended through to this side. The bed also thins out to the north and south, the whole length of the outcrop being only about 400 feet. East of the outcrop of the ore, the knoll is cut sharply off, as shown in Figure 2, by a rocky area which separates it from the mountains. It will thus be seen that the amount of ore here is limited, and it is probable that the area underlain by it does not cover more than a few acres.

Beneath the ore bed, as seen in one of the small pits that have been made on the deposit, the calcareous material is soft and partakes of the nature of a marl, while above, it is often much harder and has in many places become coarsely crystalline. The crystillization seems to have taken place in spots in the bed, and frequently bodies of crystalline material are surrounded by, and blend into a massive and softer tufa of the same composition.

The fragments of sandstone, shale and gray limestone found in this deposit are of the same nature as the beds of those rocks which comprise the mountain to the east and are undoubtedly derived from them. The pieces of limestone are so markedly different from the calcareous bed enclosing them that they cannot be confounded with it. The rock fragments are of unequal distribution in the deposit, both laterally and vertically, sometimes composing almost half of it, and sometimes being almost entirely absent. They vary from a fraction of an inch to several inches in diameter and are indiscriminately mixed.

The age of the rocks composing the part of the Havallah Range lying east of the manganese deposit is represented as Star Peak Triassic on the map accompanying the Survey of the Fortieth Parallel.^[1] As shown in the section given above they are