Actinolite is dutiable at 20 per cent. ad valorem and is not the same as asbestos.64

65

Apatite is free under the Act of 1895, p. 500, for use as manure. This is true even if the apatite is ground. Grinding does not remove it from the free list.66

Siliceous stone is a mineral substance and when ground is "advanced in value or condition" and dutiable, and not free as sand.67

Cornish stone was found to be a variety of feldspar and held not dutiable, being a crude mineral.68

Talc is non-dutiable as a crude mineral and does not come under the classification of French chalk.

69

Earth composed of oxide of iron, silica, alumina, and lime used as a polishing powder is dutiable as an "earth manufactured" at $3 per ton.70

Asphaltum is non-dutiable, coming under the classification of a crude mineral." By a curious later decision, however, it was held that asphaltum "sundried in the bed" is dutiable at $3 per ton, on the ground that it was "advanced in value or condition" by refining or "other process of manufacture."" Exposure "in the bed," to the rays of the sun would appear to be a remarkably simple process to be termed a "refining" or "process of manufacture." This decision seems highly inconsistent with the other decisions noted herein, in which picking gangue and waste out of blende, concentrating copper ore and removal of waste rock from barytes by jigging, are held not to "advance" the condition of such ores so as to make them dutiable.

Under the last subdivision of this subject no further summary is possible than the enumeration and digest of the decisions given herein; for each decision being the interpretation by a court or other proper authority as to what is included under the term mineral, mineral load, crude mineral, etc., as used in the statutes cited, the case of each particular substance must be decided by the facts relating to such substance, so that the precedent of any case does not go farther than the substance passed upon or those so similar as to be practically identical. It may be noted, however, that in all the subdivisions of the subject the cases show an

increasing tendency of the courts and other authorities to call for and rely on the expert testimony of scientific men-chemists, engineers, and geologists for aid in deciding the important cases that arise under this subject. As the quotations given above from the early cases indicate, there then existed a marked tendency in the courts to make some supposed understanding of the "mass of mankind" the basis of decisions on these questions, usually with unsatisfactory results, while later decisions arrived at by the aid of competent scientific testimony have stood and become reliable precedents.

V

Theories of ore formation; historical outline; views held by the authorities at the present day; classification of ore deposits; the planetesimal hypothesis and ore deposits.

TH

THEORIES OF ORE FORMATION

HE problem of the sources of the accumulation of metalliferous minerals in masses of such richness that they can be profitably mined is one which, from the earliest times, has attracted the attention of practical miners and geologists. It is of great inherent interest, not only on account of the intricate scientific theories involved, but also because of the practical utility of a correct understanding of the genesis of ore deposits as an aid to discovery and exploitation. These theories are often more or less directly involved in the disputed questions of mining litigation and may control the decision of the case.

In the case of Bullion Beck & Champion vs. Eureka Hill Co.,1 the following quotation by the court, from the testimony of one of the experts in the case, shows how such theories may be taken into account:

"My general conclusións are: First, that the eruption of the vast body of trachyte or porphyry, immediately east of Eureka Hill ore-bearing zone, was the primal cause of the fissuring, crushing, and buckling of the lime beds; Second, that the heat evolved by this immense mass of volcanic rock, was an active agent in driving the hot gases and mineralized solutions up through the broken and fissured zone of limestone, now known as the Eureka Hill Lode or Ore Zone. . . . Fourth, that the whole zone of ore deposits shows beyond a possibility of a doubt that the ore and quartz was deposited by chemical solutions and substitution, mainly of quartz and ore in the place of the lime dissolved out, instead of the filling of open fissures or other cavities made by the eruption."

Also in the case of Iron Mine vs. Loella Mine,2 the court says: "We come next to the position assumed by the defendants, to the effect 22 McCrary, 121 (127), 3 Fed., 368.

111 Pacific, 515 (526).

that the lode is continuous from side to side of plaintiff's location, and that the part which plaintiffs claim to be a top or apex is only an upward swell, ridge, or high point in the vein from which it descends in both directions. In support of that view evidence has been given to the effect that the ore was deposited after the tracts had come to their present position, the deposition proceeding practically at the same time and by the same agencies on the upper and eastern face of the limestone, and upon the western face of the limestone as well. . . . According to that theory the ore was deposited on the eastern and western slopes of the limestone by the same forces and in the same way and at about the same time. . . . And if it is continuous, as suggested, ... the plaintiff cannot follow it beyond the lines of its location."

The subject is of such importance that I will give a few paragraphs briefly recapitulating the older theories of deposition that have prevailed from time to time, and will continue with a somewhat detailed statement of the modern views regarding the concentration of minerals in ore-bodies; for only present-day ideas weigh with the courts in current litigation. I will conclude with a scheme of classification which is the logical outcome and summary of such investigations and theories.

The first theory of ore deposition worthy of the name was that of Werner (1750-1817), a professor in the Freiberg Mining Academy; and it was a part of his general geological doctrine, known as the Neptunian theory. According to his ideas, the whole globe was once surrounded by an ocean of water at least as deep as the mountains are high. He believed that such rocks as granite, gneiss, basalt, porphyry, schist, limestone, etc., had been precipitated from solution in this universal ocean during the earliest "chaotic" periods by chemical agency. These were followed by "transition" rocks such as graywacke, clay-slate, crystalline schist, gypsum, etc., due to both chemical and mechanical agencies, and, at the end, succeeded by rocks that were wholly mechanical deposits such as sandstone and alluvial formations.

Since all these rock formations were deposited from the water, he naturally attributed the filling of the fissures in such rocks to the same source.

He says:

"We are also convinced that the solid mass of our globe has been produced by a series of precipitations formed in succession (in the humid way); that the pressure of the materials thus accumulated was not the same throughout the whole, and that this difference of pressure and several other concur

ring causes have produced rents in the substance of the earth, chiefly in the more elevated parts of its surface. We are also persuaded that the precipitates taking place from the universal water must have entered the open fissures which the water covered. . . . that part of it which was confined to the fissures was undisturbed and deposited in a state of tranquillity its precipitate." 3

Werner's ideas as to ore deposits are commonly known as the "descension theory." He was, perhaps, the leading teacher of geology of his day and exercised great influence; so that, although "wholly irrational," his theory long predominated in geology.

In 1839 Sir Henry de la Bêche (1796-1855) published his "Report on the Geology of Cornwall, Devon, and Somerset," in which he concludes that the fissure veins (the only ore deposits of those counties) were the result of the filling of fissures in rocks by chemical deposits of substances held in solution in water which circulated in the fissures, and that this deposition was largely due to electro-chemical agency.

Among the French geologists, Élie de Beaumont (1798–1874), of the Paris School of Mines, proposed, in 1847, as a theory to account for ore deposits in veins, that the ultimate sources of such minerals are in the eruptive rocks, from which they emanate in the gaseous form, and as they pass out, through canals and fissures, they condense at greater or less distances and thus form ore deposits. The metals in veins are most often combined with certain elements such as: sulphur, selenium, arsenic, antimony, bromine, iodine, etc., called "mineralizers," which have the property of rendering the resulting compound volatile. These minerals, in the gaseous form, are also often taken up and absorbed by water and deposited from aqueous solution in the fissures; the water descending from the surface and rising again after becoming charged with mineral or being charged therewith on the upper journey. But this theory cannot possibly account for the gangue minerals which are mostly non-volatile.

Von Cotta (1808-1879), professor of geology in the Mining School of Freiberg, published in 1859 a text-book on ore deposit.s which was translated into English by Prime in 1869. He gives a fair account of the various theories of ore deposits, and, while proposing no new theory of his own, appears to lean to the idea

3 Neue Theorie von der Entstehung der Gängen, chap. vii, sec. 68 (1791); quoted in Geikie's "Founders of Geology," p. 115.