Allen Mine, Aurora Mining District, Lawrence Co., Missouri, USAi

Regional Level Types
Allen Mine	Mine
Aurora Mining District	Mining District
Lawrence Co.	County
Missouri	State
USA	Country

This shaft, at the time when last visited, in December, 1898, was 120 ft. deep. Immediately opposite, about 150 ft. to the north, was the McLeod shaft, 70 to 80 ft. deep. Both shafts passed, first, through solid limestone, from 50 to 60 feet thick. Under this, the basin-shaped ore body was struck; it rises on both sides toward the surface, and tapers out at the same time. The country rock consists of limestone and chert beds, which are horizontal and undisturbed. Close to the shaft, a deep pocket or extension of the ore body was followed to a depth of 120 ft., as is shown in the cross-section; this was not of the nature of a crevice, but more of an elongated sack or pocket, and was not traceable upward in the shaft, above the main body of ore. This channel-like deposit extends in a direction a little north of east, in conformity with the general trend shown in figure 172. The face of ore is from 8 to 10 feet high; it is underlain and overlain by limestone. The surface of the limestone is very irregular, especially in the foot-wall, where hammocks and ridges or bars separate depressions which contain large pockets of ore; on the sides of the basin, the ore body cuts diagonally across the strata at an angle of sometimes as much as 20° with the horizontal. The ore body is soft in places, consisting of chert fragments surrounded by clay; elsewhere it is hard, and is composed of blocks and layers of chert and limestone, the latter partially decomposed. The metalliferous minerals are chiefly galena, with a little blende and silicate in the lowest levels. The galena is generally near the top or bottom of the run, with limestone blocks between. Tallow clay and calcite also occur here; but very little pyrite, and no dolomite, were observed. Joint planes were seen running diagonally across the deposit, in a northeast to southwest direction; a few also ran from north to south.