The Economic Aspect of Geology Part 26

In the Central Plateau of France the numerous antimony deposits are stibnite veins cutting granites and the surrounding schists and sediments. An origin related in some way to hot ascending solutions seems probable.

The deposits of the National district of western Nevada, the most important war-developed antimony deposits of the United States, consist of stibnite veins with a gangue of fine-grained drusy quartz, cutting through flows of rhyolite and basalt. They are intimately related to certain gold- and silver-bearing veins, and all are closely a.s.sociated with dikes of rhyolite, which were the feeders to the latest extrusion in the district. The wall rocks have undergone alteration of the propylitic type. These relations, and the presence of the mercury sulphide, cinnabar, in some of the ores (see pp. 258-259), suggest an origin through the work of ascending hot waters or hot springs. These waters probably derived their dissolved matter from a magmatic source, and worked up along vents near the rhyolite dikes soon after the eruption of this rock.

In the weathering of antimony deposits, the stibnite usually alters to form insoluble white or yellowish oxides, which are sometimes called "antimony ocher." These tend to acc.u.mulate in the oxide zone through the removal of the more soluble accompanying minerals. Secondary sulphide enrichment of antimony deposits, if it occurs at all, is negligible.

a.r.s.eNIC ORES

ECONOMIC FEATURES

About two-thirds of the a.r.s.enic consumed in recent years has been used in agriculture, where various a.r.s.enic compounds--a.r.s.enic trioxide or "white a.r.s.enic," Paris green, lead a.r.s.enate, etc.--are used as insecticides and weed killers. a.r.s.enic compounds are also used in "cattle-dips" for killing vermin. The only other large use of a.r.s.enic is in the gla.s.s industry, a.r.s.enic trioxide being added to the molten gla.s.s to purify and decolorize the product. Small quant.i.ties of a.r.s.enic compounds are used in the preparation of drugs and dyeing materials, and metallic a.r.s.enic is used for hardening lead in shot-making.

The princ.i.p.al a.r.s.enic-producing countries are the United States, Germany, France, Great Britain, Canada, and Mexico. Spain, Portugal, j.a.pan, and China are also producers, and recent trouble with the "p.r.i.c.kly-pear" pest in Queensland, Australia, has led to local development of a.r.s.enic mining in that country. For the most part, European production has been used in Europe and American production in the United States.

a.r.s.enic is recovered almost wholly as a by-product of smelting ores for the metals. The potential supply is ample in most countries where smelting is conducted, but owing to the elaborate plant required to recover the a.r.s.enic, apparatus is not usually installed much in advance of the demand for production. Rapid expansion is not possible.

Before the war the a.r.s.enic needs of the United States (chiefly agricultural) were supplied by a few recovery plants in the United States, Mexico, and Canada. Several large smelters had not found it profitable to install recovery plants, as the market might have been oversupplied and prices were low. During the war, with the extensive demand for insecticides for gardening, there was a considerable deficiency of a.r.s.enic supplies. With rising prices production was stimulated, but was still unable to meet the increased demand. This situation resulted in regulation of the prices of white a.r.s.enic by the Food Administration.

Production of a.r.s.enic in the United States comes chiefly from smelters in Colorado, Washington, Utah, Montana, and New Jersey. Small amounts are produced by a.r.s.enic mines in Virginia and New York. A Mexican plant at Mapimi has been shipping important quant.i.ties to the United States.

The plant at Anaconda, Montana, is expected to produce an ample supply in the future.

The United States is entirely independent in a.r.s.enic supplies and will probably soon have an exportable surplus. Export trade, after the reconstruction period, will probably meet compet.i.tion from France and Germany where production was formerly large.

GEOLOGIC FEATURES

a.r.s.enic-bearing minerals are numerous and rather widely distributed, but only a few of them are mined primarily for their content of a.r.s.enic.

a.r.s.enopyrite or "mispickle" (iron-a.r.s.enic sulphide) has been used intermittently as a source of white a.r.s.enic in various places,--notably at Brinton, Virginia, and near Carmel, New York. The former deposits contain a.r.s.enopyrite and copper-bearing pyrite impregnating a mica-quartz-schist, adjacent to and in apparent genetic relation with aplite or pegmat.i.te intrusives. In the latter locality a.r.s.enopyrite is found a.s.sociated with pyrite in a gangue of quartz, forming a series of parallel stringers in gneiss close to a basic dike.

The orange-red sulphides of a.r.s.enic, orpiment and realgar, are formed both as primary minerals of igneous source and as secondary products of weathering. They are rather characteristic of the oxide zones of certain a.r.s.enical metallic ores, and are believed in many cases to have formed from a.r.s.enopyrite. They are mined on a commercial scale in China.

The great bulk of the world's a.r.s.enic, as previously stated, is obtained as a by-product of smelting operations. The enargite of the b.u.t.te copper ores (pp. 201-203) contains a considerable amount of a.r.s.enic, a large part of which will be recovered from the smelter fumes by new processes which are being installed. The gold-silver ores of the Tintic district (pp. 235) also yield important amounts, the a.r.s.enic-bearing minerals being enargite and tennant.i.te (copper-a.r.s.enic sulphides) and others. The silver ores of the Cobalt district of Ontario (pp. 234-235), containing nickel and cobalt a.r.s.enides, produce considerable a.r.s.enic. Many other metallic ores contain notable amounts of a.r.s.enic, which are at present allowed to escape through smelter flues, but which could be recovered under market conditions which would repay the cost of installing the necessary apparatus.

BIs.m.u.tH ORES

ECONOMIC FEATURES

Bis.m.u.th metal is used in alloys, to which it gives low fusibility combined with hardness and sharp definition. Bis.m.u.th alloys are employed in automatic fire sprinklers, in safety plugs for boilers, in electric fuses, in solders and dental amalgams, and in some type and bearing metals. Bis.m.u.th salts find a considerable application for pharmaceutical purposes, especially in connection with intestinal disorders, and the best grades of bis.m.u.th materials are used for this purpose. The salts are also used in porcelain painting and enameling and in staining gla.s.s.

Bolivia is the most important producer of bis.m.u.th ore. The output is controlled entirely by British smelting interests. An important deposit exists in Peru, the output of which is limited by the same British syndicate. Considerable bis.m.u.th is produced in Australia, Tasmania, and New Zealand, all of which likewise goes to England. Germany before the war had three smelters which produced bis.m.u.th from native ores in Saxony; bis.m.u.th was one of the few metals of which Germany had an adequate domestic supply. Recently southern China is reported to be mining increasing amounts of bis.m.u.th.

The United States produces the larger part of its bis.m.u.th requirements, chiefly from plants installed at two lead refineries. A further installation would make this country entirely independent of foreign supplies if occasion required. Imports, from England and South America, have been steadily declining, but during the war were somewhat increased. The United States does not export bis.m.u.th so far as known.

GEOLOGIC FEATURES

The princ.i.p.al minerals of bis.m.u.th are bis.m.u.thinite (bis.m.u.th sulphide), bis.m.u.t.i.te (hydrated carbonate), bismite or bis.m.u.th ocher (hydrated oxide), and native bis.m.u.th.

The native metal and the sulphide are believed to be formed mainly as primary minerals of igneous origin. In the deposits of New South Wales they are found a.s.sociated with molybdenite in quartz gangue, in pipe-like deposits in granite. The oxide and the carbonate are probably products of surface weathering. The Bolivian deposits contain the native metal, the oxide, and the carbonate, a.s.sociated with gold, silver, and tin minerals, in one locality in slates and in another locality in porphyry. The origin is not well known.

In the United States, the sulphide, bis.m.u.thinite, is found in the siliceous ores of Goldfield, Nevada (p. 230), and in minor amounts in a great number of the sulphide ores of the Cordilleran region. The ores of the Leadville and Tintic districts (pp. 219 and 235) yield the larger part of the United States production, the bis.m.u.th being recovered as by-product from the electrolytic refining of the lead bullion. Large amounts of bis.m.u.th pa.s.s out of the stacks of smelters treating other western ores, and while it would not be cheap nor easy to save the bis.m.u.th thus lost, it could probably be done in case of necessity.

CADMIUM ORES

ECONOMIC FEATURES

Cadmium is used in low melting-point alloys--as, for example, those employed in automatic fire-extinguishers and electric fuses,--in the manufacture of silverware, and in dental amalgams. During the war the critical scarcity of tin led to experiments in the subst.i.tution of cadmium for tin in solders and anti-friction metals. Results of some of these experiments were promising, but the war ceased and demands for tin decreased before the cadmium materials became widely used. Future developments in this direction seem not unlikely. Cadmium compounds are used as pigments, particularly as the sulphide "cadmium yellow," and to give color and l.u.s.ter to gla.s.s and porcelain. Cadmium salts are also variously used in the arts, in medicine, and in electroplating.

Practically the entire cadmium output of the world comes from Germany and the United States. In addition, England produces a very small quant.i.ty. Before the war Germany produced about two-thirds of the world's total, and supplied the European as well as a considerable part of the United States consumption. During the war the United States production increased three to four fold, imports ceased, and considerable quant.i.ties were exported to the allied nations in Europe and to j.a.pan. At present the United States is entirely independent as regards cadmium supplies. Production is sufficient to supply all the home demand and to permit exports of one-third of the total output. A considerable number of possible cadmium sources are not being used, and the production is capable of extension should the need arise.

GEOLOGIC FEATURES

Nearly the only cadmium mineral known is the sulphide, greenockite, but no deposits of this mineral have been found of sufficient volume to be called cadmium ores. Sphalerite almost always contains a little cadmium, probably as the sulphide; and in zinc deposits crystals of sphalerite in cavities are frequently covered with a greenish-yellow film or coating of greenockite. These coatings have probably been formed by the decomposition of cadmium-bearing zinc sulphide in the oxide zone, the carrying down of the cadmium in solution, and its precipitation as secondary cadmium sulphide. The zinc oxide minerals in the surficial zone also are sometimes colored yellow by small amounts of greenockite.

In the zinc ores of the Joplin district of Missouri, cadmium is present in amounts ranging from a trace to 1 per cent and averaging 0.3 per cent.

Germany's cadmium is produced by fractional distillation of the Silesian zinc ores, which contain at most 0.3 per cent cadmium. In the United States there are large potential sources in the zinc ores of the Mississippi valley, and considerable cadmium is recovered in roasting them. Much of the American cadmium is also obtained from bag-house dusts at lead smelters.

The general geologic conditions of the cadmium-bearing ores are indicated in the discussion of lead and zinc deposits in an earlier chapter.

COBALT ORES

ECONOMIC FEATURES

Cobalt finds its largest use in the form of cobalt salts, employed in coloring pottery and gla.s.s and in insect poisons. Cobalt is also used in some of the best high-speed tool steels. "Stellite," which is used to a limited extent in non-rusting tools of various sorts, and in considerable quant.i.ty to replace high-speed tool steels, is an alloy of cobalt, chromium, and small quant.i.ties of other metals. Considerable experimental work has been done on the properties and uses of cobalt alloys, and their consumption is rapidly on the increase.

Cobalt is an item of commerce of insignificant tonnage. There are only two countries, Canada (Ontario) and the Belgian Congo, which produce noteworthy amounts. The Katanga district in the Congo produces blister copper that contains as much as 4 per cent of cobalt, though usually less than 2 per cent. This product formerly went to Germany, and now goes entirely to Great Britain. Just how much cobalt is saved is unknown, but probably several hundred tons annually. It is probable that most of the cobalt in these ores will be lost on the installation of a leaching process for recovery of the copper. Canada exports most of its product to the United States, though the amount is small. Domestic production in this country has been too small to record. The United States has been dependent on imports from Canada.

GEOLOGIC FEATURES

The princ.i.p.al cobalt minerals are smalt.i.te (cobalt a.r.s.enide), cobalt.i.te (cobalt-a.r.s.enic sulphide), and linnaeite (cobalt-nickel sulphide). Under weathering conditions these minerals oxidize readily to form asbolite, a mixture of cobalt and manganese oxides, and the pink a.r.s.enate, erythrite or "cobalt bloom."

Cobalt minerals are found princ.i.p.ally in small quant.i.ties disseminated through ores of silver, nickel, and copper. The production of Canada is obtained mainly as a by-product of the silver ores of the Cobalt district (described on pp. 234-235), and smaller amounts are recovered from the Sudbury nickel ores (pp. 180-182). The cobalt of Belgian Congo is obtained from rich oxidized copper ores which impregnate folded sediments (p. 205).

MERCURY (QUICKSILVER) ORES

ECONOMIC FEATURES

Uses of mercury are characterized by their wide variety and their application to very many different phases of modern industry; they will be named here in general order of decreasing importance. About one-third of the mercury consumed in this country goes into the manufacture of drugs and chemicals, such as corrosive sublimate, calomel, and glacial acetic acid. Mercury fulminate is used as a detonator for high explosives and to some extent for small-arms ammunition--a use which was exceedingly important during the war, but is probably of minor consequence in normal times. Mercuric sulphide forms the brilliant red pigment, vermilion, and mercuric oxide is becoming increasingly important in anti-fouling marine paint for ship-bottoms. Either as the metal or the oxide, mercury is employed in the manufacture of electrical apparatus (batteries, electrolyzers, rectifiers, etc.), and in the making of thermostats, gas governors, automatic sprinklers, and other mechanical appliances. Mercuric nitrate is used in the fabrication of felt hats from rabbits' fur. In the extraction of gold and silver from their ores by amalgamation, large amounts of metallic mercury have been utilized, but of late years the wide application of the cyanide process has decreased this use. Minor uses include the making of certain compounds for preventing boiler-scale, of cosmetics, and of dental amalgam.