Midnight Mine [1], Midnight vein, Oatman, Oatman Mining District, Black Mountains, Mohave County, Arizona, USAi

Regional Level Types
Midnight Mine [1]	Mine
Midnight vein	Vein
Oatman	Town
Oatman Mining District	Mining District
Black Mountains	Mountain Range
Mohave County	County
Arizona	State
USA	Country

MIDNIGHT MINE.

The Midnight mine is situated in the hills 1½ miles northwest of Vivian, at an elevation of 2,500 feet, and is accessible by wagon road. It is owned by the Mohave Gold Mining Company, and has been producing moderately since about 1900. For some time it paid the running expenses of the Leland mine, which were large.

The mine is developed to a depth of 50 feet by inclined shaft, drifts, and stopes and is equipped with a gasoline hoist; the management has just begun sinking the shaft 300 feet deeper.

The country rock is the green chloritic andesite. It is intruded by basic and acidic dikes near by and is cut by a marked sheeting which trends N. 10° W. and dips 75° W. and by a close cross sheeting which dips steeply to the north. One of the basic dikes, a fine-grained greenish rock, about 40 feet in width, forms the foot wall. About 300 feet northeast of the mine, on higher ground, occurs a closely banded bluish to light-gray and greenish mottled 2 to 3 foot vein composed of fine-grained siderite containing some lime and manganese. It resembles rhyolite with banded or flow structure and may have replaced a dike in the fissure it now occupies.

The Midnight vein, which is the foot-wall member of a north-south lode, 100 feet wide, strikes N. 15° W. and dips 30° to 40° W. It is about 3½ feet in width and consists principally of quartz, with some calcite, fluorite, and adularia. Its foot-wall, portion, for a width of 3 or 4 inches, contains crudely banded red and green fluorspar, and toward the foot wall the quartz becomes dark and dense, of a flinty nature, and contains a few crystals of pyrite.

The vein has been worked from the surface almost to the bottom of the mine and longitudinally for a distance of about 120 feet, mainly on the south side of the shaft, and in this extent has averaged about $18 a ton in gold. The production has been considerable for a mine of its size, that on one side of the shaft alone amounting to $18,000. Where now worked in the bottom of the mine the ore is of low grade, running about $7 in gold to the ton, and consists of a mixture of partly altered soft country rock traversed by stringers and veinlets of calcite and quartz.