cracks in the earth's crust, and secondly to the agencies which have caused these fractures or breaks to be filled more or less continuously with the ores of the valuable minerals.1

Longitudinal Extent. The extent of veins across the country is so indefinite that it would be folly to make any statement with regard to it here. Sometimes a vein runs for a number of miles ; other times it seems to be impossible to follow it but a short distance; but no thoroughly trained man can ever mistake a true fissure vein for anything else. There is always such a continuity of the original crack and of the so-called "secondary" mineral matter—that is, mineral matter which was certainly deposited after the break occurred by the hot waters and vapors which have come up through the fissure that it presents in the great majority of cases an unmistakable and characteristic appearance. This continuity on the strike and dip of the vein can usually be shown to exist, unless, of course, the vein after its formation has been subjected to faulting, as already described.2

Generally speaking, it would seem to the author that an ore body, to be regarded in the eye of the law as a "lode," and which will be given all the legal attributes which belong to true lodes, must not only possess reasonable continuity, but must in itself represent some well defined and reasonably regular main channel of mineralization, through which the hot waters and vapors ascended and in which or along which they deposited their mineral solutions. This is an almost infallible test. Thus a "pipe" of ore, representing presumably an old geyser vent and having but little lateral extent, though having great depth, would fall within the classification of true lodes, and the owner of the apex of such a deposit would be entitled to follow it outside of his boundary lines. On the other hand a mineralized "shoot" or run of ore," which in itself does not represent a principal channel of mineralization, cannot be regarded in a mining, geological or legal sense as a true lode. Many terminable spurs and irregular bodies of ore often extending but short distances, which may, however, be connected with such main channels of mineralization, are thus excluded from the classification of lodes and "the law of the apex" cannot apply to them. These must, there

66

1 With regard to the causes which have produced these deep reaching fissures see

p. lx.

2 For the explanation of the terms "strike" and "dip" of a vein see Chap. XV., Div. I., A, p. 441, post.

tore, fall within the classification which will be treated of under the title "Unstratified Mineral Deposits which are Irregular," and the same rules of law which are applicable to this class will be applicable to them.

(b.) Contact Deposits which are so Continuous as to be regarded as Lodes.

It is now necessary to speak of an intermediate class of deposits which do not lie in real fissures and in a sense are perhaps not true lodes, but which in their general characteristics are so like them that they are so regarded in a legal sense. These are what are generally known as Contact deposits. They are usually found between or very close to the junction between two different formations or kinds of rock. There are examples of a contact deposit between sedimentary strata where the so-called vein or lode adheres closely to the line dividing two strata,- for instance, two beds of limestone. Nothing is more unlikely than that these deposits were formed by sedimentary action at the time when the limestone was formed; on the contrary, it is practically certain that the mineralized waters ascended, as in the case of veins, from some inferior region along this line of contact, finding in it a convenient pathway of escape, and deposited along it their load of mineral matter. In so doing they probably replaced very. considerable portions of the limestone, the time of mineralization having been subsequent to the consolidation and tilting of the limestone and the adjacent rocks. Now this deposit is so continuous and hugs this contact so closely that it as a whole can be regarded as a lode deposit. If, however, the ore or mineral matter should be discontinuous, and the limestones should be found to frequently lie one upon the other, with no intervening mineralized matter or break, it should not, in the opinion of the author, be properly regarded as a lode (although it would still be a contact deposit), and what is known as the "law of the apex" should not rule.

Another familiar case-although it is not on government land is the famous deposits of copper in a conglomerate bed in Michigan. It would seem that these generally should be regarded as lode deposits, although the copper is found in what was originally nothing more or less than an old bed of pebbles now 1 Very often a fault produces a so-called contact deposit.

cemented together, or conglomerate bed. This bed is now tilted to an angle of about forty degrees, and has been greatly metamorphosed by the heat of the adjacent eruptive rocks. It is practically certain, however, that this copper was not deposited at the time this was an unconsolidated pebble deposit, but that it got into the stratum subsequently, and probably after the rocks had been tilted. The hot mineralized waters found in this a most convenient place for their ascent, and one which was favorable for the deposition of the mineral matter which they carried.

As to how nearly the characteristics of such a deposit must approach a true fissure or vein deposit in order to be considered as such from a legal point of view is very difficult to say; but it may be said in a general way that they must always present the characteristic of continuity of ore or subsequently deposited mineral matter. This ore need not be rich, and indeed may be very poor, and the deposit for a long distance may be practically barren; but some subsequently deposited mineral or minerals must be proved to exist very continuously between the adjacent rocks before such a deposit can be classed in a mining or legal sense as a lode, and it is again suggested that the deposit must in itself represent some well defined old channel of mineralization through which the waters and vapors ascended with their load of mineral matter from the source from which they obtained it. The formations must not lié tight together and undisturbed upon each other for considerable distances; for this feature alone would be sufficient to bring the deposit within the class which will be next described. Again, there are some contact deposits next to eruptive rocks which are very difficult to classify, both in a mining and legal For instance, a dike has come up through some preexisting rock, and the ore has been subsequently deposited along

sense.

the side of this dike or in the country rock close to it. It is always perfectly easy to follow along the wall of this dike, and one is rewarded by finding from time to time bunches of ore which in some cases are very rich. The dike may be only small, a foot or a few feet in thickness, or it may be perhaps a hundred feet in thickness. Now, if it can be shown that the dike itself is mineralized more or less continuously, although it may not in itself be pay ore, it would seem that such a deposit can be located as a lode or fissure vein deposit; and it is generally true that such deposits are so located, although it by no means follows that all such deposits should be regarded as true lodes. It is possible, however, in many cases to prove continuity, in that the dike itself frequently carries a small amount of mineral, or it is easy to find between the dike and the adjoining country a little stringer or thin deposit of ore, worthless in itself, but valuable in showing the continuity of the deposit. Often a vein (true fissure) will follow along a line of weakness produced by a pre-existing dike for some distance, then break away from it. This would be distinctly of the former class, and is not now referred to.

At other places there may be a large and very continuous body of ore following across country the contact of some eruptive rock - for instance, granite and porphyry - and some other rock, eruptive or sedimentary,- for instance, limestone. This ore may owe its origin in the first place to the eruption of the granite through the limestone, and afterward to the passage of mineralized waters between the contact of the eruptive and the sedimentary rock, along which contact they have ascended. These waters may have leached out great quantities of both rocks, but especially of the rock which would yield most readily to such influences,—as, for example, in this case of limestone,- and have deposited in its place, for long distances next to this contact, huge bodies of ore or mineralized matter. Such deposits could not be regarded in any other light than as a lode or vein, though having an origin in many features geologically different from it. In order to be so regarded, the simple rule with regard to deposits of this class is, that they must always show a very decided continuity of ore or mineral matter deposited subsequently to the intrusion of the eruptive through the pre-existing and overlying rocks. Or in cases where there are no dikes or irregular intrusions of eruptive material, and the ore is found occupying a position between two

dissimilar formations, these must be very continuously divided by such ore or subsequently deposited mineral matter before the deposit or contact can be called in a legal sense lode or a vein, and pos sess the legal attributes of such.

From what has been said, it is clear that all contact deposits cannot be regarded as lodes. In fact, a very large number of valuable mineral deposits should certainly not be so regarded, simply because of the marked lack of continuity of mineral matter which has been deposited subsequently to the formation of adjacent rocks. This class will be treated of in the next division.

There are other classes of ore deposits which deserve reference in passing; that is to say, those which are found in or around some neck of volcanic material which has welled up from below through any kind of rock composing the hard so-called "crust" at that particular locality. These may be regular or irregular contact deposits around the edge, or the central eruptive mass itself may have been shattered by volcanic forces, and true fissure veins thus established in it. These fissures in some cases may have been subsequently filled with dikes of other eruptive material, or in others with the solutions from hot waters ascending through them, and forming deposits of the valuable ores. These deposits usually give no trouble, and should be properly classified in the great majority of cases without difficulty.