Petroleum
The occurrence of petroleum in the Redington quicksilver-mine, New Idria, California, is reported by Luther Wagoner. He says: ‘‘ Mineral-oil occurs in considerable quantity, a barrel of forty gallons being collected in one drift. It was used for lubrication of the machinery.”
Prof. Egleston, writing of the quicksilver-mines in northern California, says: “ At the Rattlesnake mine, near Pine Flat, where large quantities of metallic mercury are found, the rock contains so much petroleum that it has been necessary to make special arrangements to burn the carbides of hydrogen, since the distillation of the petroleum causes an extra quantity of poor soot to be formed in the condensation-chambers.”
At the zinc- and lead-mines near Shullsburg, Wisconsin, thin partings or beds of brown shale, highly charged with petroleum, are found in the Trenton limestone. Prof. Blake, discussing the peculiar occurrence of this shale, known as the “ oil- rock,” says: “We find that this petroleum-shale, this horizon of hydrocarbons, is to-day the chief lower horizon of deposition of the lead- and zinc-ores. Certainly, if this shale did not influence or determine the original primary accumulation of the ores, it appears to have exerted a very important influence upon the secondary or later deposition, from solutions percolating downwards.”
In the mines at Silver Reef, Utah, an oily substance, supposed to be petroleum, is reported to have occurred in the refractory ores at water-level.
Rudolf Keck notes the association of organic matter with ore-deposits. He says: “ Organic matter occurs in the state of asphaltum in the cinnabar mines in the Bavarian Palatinate ; in that of petroleum, in the mines of California, Nevada and Hungary; in that of anthracite and graphite, in mines in Transylvania, Portugal, Derbyshire, Calcutta, Saxony, Baden, etc.”
Bitumen
The occurrence of bitumen, and its influence in the formation of the zinc- and lead-deposits in the Cherokee limestone, in Southwest Missouri, has already been discussed.
Becker notes the existence of bitumen in the Manhattan, Knoxville, Phoenix, Oathill, Manzanita, Great Western and Great Eastern quicksilver-mines, and also at Sulphur Bank, California. At the Phoenix mine, a peculiar non-oxygenated hydrocarbon (napalite), with 90 per cent, of carbon and 10 per cent, of hydrogen, occurs quite abundantly.
Luther Wagoner, in an article on the geology of the quick-silver-mines of California, says : “ Oil (petroleum), more or less oxidized, is observed in all mines of quicksilver on this coast, and in general is found as bitumen or a thick tar.”
Prof. Christy thus describes the occurrence of bitumen at New Almaden, Cal.: “The ore at New Almaden is cinnabar. Native quicksilver occurs also; but, as a rule, in small quantities only. Pyrite occasionally accompanies the ore. Bitumen is quite common, sometimes as a fragile, black, lustrous solid, resembling soft bituminous coal, but melting easily, like tar; at other times it occurs in the vugs of the gangue, in a liquid state, like coal-tar. I have found lumps of apparently pure cinnabar from the New Almaden to give a voluminous residue of pulverulent charcoal, when subjected to sublimation out of contact with the air. This would seem to show that the bituminous substance is intimately associated with the cinnabar.”
Marsh-Gas (CH4)
In the quicksilver-mines of California marsh-gas was discovered by Becker. In the Phoenix mine, on the 150- and 300-ft. levels, inflammable gas, mainly composed of marsh-gas, issues from cracks in the rock. At Sulphur Bank, California, 79 parts of marsh-gas were found in 1000 parts of the gases escaping with the ore-depositing waters.
Flows of gas under heavy pressure were struck in the deeper levels of the Silver-Islet mine, Lake Superior. Subsequently, in extending the levels, vugs and cavities in the vein were found, lined with crystals of galena and calcite, in which the gas had probably been stored. In sinking the shaft, gas was also encountered in the slate, and it appears to have pervaded the country-rock below the 8th level (440 ft., vertical depth). The gas was associated with small flows of strong, acrid mineral-water, carrying much calcium chloride. It burned with a purple, blue, or yellowish flame, and was supposed to be light carburetted hydrogen, but it was never analyzed.
Small quantities of hydrocarbon-gas are stated by Mr. B. Tibbey to have been struck in following the vein on the 300-ft. level of the Illinois mine, Walkerville, Butte City, Montana. The gas burned with a bright-yellow flame, like ordinary illuminating gas. This occurrence is remarkable, as the vein occurs in granite.
Review of the Action of Volatile Hydrocarbons.—In the Joplin, Mo., mines, the greater part of the bitumen set free by the extensive subterraneous erosion of the lime strata is still preserved in the ore-bodies below water-level, owing to the primary deposition having been effected by mineral-solutions of normal temperature. The same is also true of the petroleum occurring with the zinc-ore in the oil-rock in the Trenton limestone in Wisconsin, to which reference has been made. But in many ore-deposits in other mining-regions the heat accompanying the deposition has been so great, and the chemical activities so intense, that every trace of volatile hydrocarbons has been destroyed.
Petroleum contained in the strata may be decomposed by (1) destructive distillation, due to the earth-temperatures or to the heat of the ascending mineral-solutions; (2) by oxidation, the carbon and hydrogen forming carbon-dioxide and water; and (3) by the action of sulphur, which dehydrogenizes the oil.
Petroleum and similar hydrocarbons, when heated and subjected to the action of sulphur at temperatures (in the case of the heavier oils) far below that at which distillation occurs, are rapidly decomposed, with formation of sulphuretted hydrogen and of oils with a greater proportion of carbon than the original oil; or, if the sulphur be in excess, carbon is in some instances deposited.
The role of the volatile hydrocarbons in the primary formation of mineral-deposits, especially where the deposition is due to igneous disturbances, has not received the attention it deserves. Investigation is needed of the action that marsh-gas and other hydrocarbon-gases exert in the deposition of ores; particularly in the formation of deposits of cinnabar, which are frequently associated with bituminous shale, bitumen and volatile hydrocarbons.
Marsh-gas has a theoretic reducing power one-half that of hydrogen and fifty per cent, greater than that of pure carbon. In the formation of ore-deposits, directly induced by igneous action, temperatures must inevitably occur in the depths of the strata, such that gaseous hydrocarbons would act with great energy in the deoxidation and precipitation of the metals. Under like conditions, petroleum, and the volatile carbon compounds with high boiling-points, would exert a reducing power but little inferior, and, from the high specific gravity of their vapor, would displace steam and all other gases of less relative weight.
The Relative Reducing Power of Minerals