Observations on the rich parts of the lodes of Cornwall ... Translated from the French, by J. H. Collins, etc

Front matter

OBSERVATIONS ON THE RICH PARTS OF THE LODES OF CORNWALL, Their Form, and their Eelations with the Directions of the Stratigraphic Systems. B. PROFESSOR L. MOISSENET, OF THE ■' ECOLE DES MINES," PARIS, HONORARY MEMBER OF THE MINERS' ASSOCIATION OF CORNWALL AND DEVON, THE ROYAL GEOLOGICAL SOCIETY OF CORNWALL, Etc, Eic. TRANSLATED FROM THE FRENCH BY J, H. COLLINS, F.G.8., HON. SECRETARY TO THE MINERS' ASSOCIATION OF CORNWALL AND DEVON. THE ROYAL INSTITUTION OF CORNWALL, AND THE MINERALOGICAL SOCIETY OF GREAT BRITAIN AND IRELAND ; AUTHOR OF A HANDBOOK TO THE MINERALOGY' OF CORNWALL AND DEVON. ETC, Etc. LONDON : SIMPKIN, MARSHALL, AND Co., STATIONERS' HALL COURT. TRURO -. LAKE AND LAKE, PRINCES STREET. 1877. All rights reserved. TRANSLATOR'S

Preface

. The Eeport of the Council of the Miners' Association of Cornwall and Devon, in June 1874, in recommending Frofessor Moissenet for election as an Honorary Life Member, contained the following reference to his works. " M. Moissenet, the distinguished French Mining Engineer, has lately written some valuable works on Lode-Mining, and of one of these, which treats especially on the veins of Cornwall, it is proposed to publish an abstract for the use of the members of the Association. This abstract will be made by your Honorary Secretary (Mr. J. H. Collins), and it will be submitted to M. Moissenet before publication." In accordance with this announcement, I commenced the abstract in question, but I soon found that the work was already so well condensed that very little abridgement was possible, if any considerable proportion of its usefulness was to be preserved.

Under these circumstances, and after renewed communications with the author, I determined to make a complete translation, and as the work in its complete form was too large to be issued in the proceedings of the Miners' Association, I was compelled to undertake the whole responsibility — pecuniary and otherwise. A considerable proportion of the cost is, however, secured by the subscription list which appears at the end of the volume, and I trust the book in its present form may prove so useful to students that the whole edition — which is limited to 400 copies — will be soon off my hands. In preparing this translation I have, as was to be expected, sometimes met with words having in their applications to mining, no exact English equivalents, as for instance, exploitation, gite, cannelure, allure, roideur, and plongement.

The last two have Translator's Preface. generally b een translated underlie and dip respectively, but the former term is manifestly inapplicable as applied to the typical case (unusual I admit) of a vertical fissure ; and the latter is a word used in a quite different sense by all geologists, and a majority of miners. I believe our mining language would gain much in precision if all these words could be naturalized. It is possible that some readers may discover that I have followed the French idiom somewhat too closely in a few in stances ; I am quite aware that this is the case but I will urge in my own defence that it is more conducive to an exact appreciation of the author's meaning than a too free translation. In one respect the book is more valuable than the original French edition, as it contains an appendix A (with plate,) which was not in that edition.

This appendix explains briefly the numerous references to the Systems and the Theories of M.Elie de Beaumont — a subject but little known hitherto to English Mining Students. The convenience of getting text and plates all into one volume will, I believe, fully compensate for the reduced scale of the plates — which in the original edition were formed into a quarto atlas. J. H. COLLINS, Truro, June 19, 1877. V, AUTHOR'S

PREFACE.

. Twenty-two years ago, I visited England for the first time ; I was then a student provided with the varied and general instruction to be acquired at the " Ecole des Mines," and was anxious to get some, and any, practical knowledge. The magnitude of the underground and surface workings of the Cornish mines impressed me deeply, and having had a glimpse of the enormous number of " mining facts " concentrated in the county of Cornwall, and of the large supply of infor mation already treasured in the local scientific records, I resolved to come over again to such a grand practical school. Thus I was led to take a peculiar interest in the study of metalliferous deposits, and was struck with the desire to become a devoted, and if possible, a useful member of the mining community. Circumstances favored my object; at home, my eminent'' masters, Mr. L. Elie de Beaumont, and my chief in the Labora tory of the School, Mr L. E. Eivot, gave me a constant support, so that I could then almost every summer interweave my official duties with the practice of mining in France and with studies abroad, and especially in Cornwall.

On the other hand, I had from the commencement met in England with an invaluable patron, Mr. Eobert Hunt, who introduced me to the world of the mines. I wish I might better state here all the scientific and moral assistance I derived from him throughout the long course of my enquiries. I wish also to acknowledge my indebtedness to the mine owners, managers, agents, and others who constantly facilitated my studies in Corn wall and Devon, among them I cannot refrain from inserting here the name of my most venerated friend, the late W. Jory Henwood. Author's Preface. VI My labours, and some troubles almost unavoidablv connected with much travelling underground, have already been amply repaid by the welcome given to the French edition of this work, and the honours granted me by the Eoyal Geological Society of Cornwall, the Eoyal Cornwall Bolyteehnic Society, the Eoyal Institution of Cornwall, and the Miners' Association of Cornwall and Devon.

The present translation originated in a resolution of the Council of the Miners' Association to publish an abstract of my "Etudes, parties riches," in its proceedings, and has reached its present complete and elaborate form through the talented zeal and skilful pen of the Honorary Secretary, Mr J. H. Collins. I have carefully reviewed the proof sheets in the course of printing, but I confess that, from the translator's ability, I have had but little share in the present work. L. Moissenet. Paris, June 16th, 1877. TABLE OF CONTENTS.

Introduction

. Unequal distribution of mineral substances in lodes — necessity for careful observations (1). The mineral contents of lodes subject to variation when the nature of the "country" changes (2). Action of physical as well as chemical causes in the formation of lodes— form of the rich parts especially due to the mechanical element (3). References to former writers (4). Object of the present work (5). CHAFTEE I. I. — Rich and poor parts of lodes, different kinds of riches (7). II. — Different kinds of rich parts, as courses of ore, shoots, bunches, branches, floors, carbonas (8). III. — General Characters of the Rich Parts. — Junctions, of lodes, intersections, &c, consideration of a single lode in a single containing rock (12). Underlie of the rich parts, those parts of a lode ivhose inclinations approach most nearly to the vertical, are always the most productive (14).

Moderate Hardness. In Cornwall the rich parts are generally enclosed in rocks of moderate hardness (14). Dip — the metalliferous hands or zones often dip in the same direction as the enclosing roclcs (18). Good bearing. Importance of this character recognised by Capt. Chas. Thomas in 1859 (19). Not sufficient to determine the mean direction of a lode — lodes subject to great variations in direction, and at the same time in size and in composition ; a change of direction of only 5° or 7° may destroy the value of a lode (20). Modes of working lodes in Cornwall, and of representing the workings on three plans drawn at right angles (20). Lodes subject to inflexions of two kinds known as turns or warps, and great turns (21), the bearing of the rich parts is generally that of the Stratigraphic System with lohich the initial fracture of the lode is connected (23).

IV. — Mutual Relations of the Four General Characters. — Distinction between normal and accessory riches ; all four characters apply to the normal rich parts, they may also apply, one or more, to the accessory rich parts (25). Two kinds of lodes (Fc Fa) differingin the direction of their underlie (28). The four general characters result from the fracture of strata of different qualities by a force acting in a straight line, and they determine the conditions of the normal rich parts in the deposits in question (30). Table of Contents. VIII 1 II Ill 6. e. d. e IV CHAPTEE II. Summary of Chapter I (31), object of the Second Chapter (32). ■General Considerations.— Principal physical, and chemical causes which appear to have effected the deposition of minerals in lodes (32). Changes of pressure and temperature, re-actions between different fluids upon each other and upon the walls, electro-magnetism (33).

Formation of initial fissures of two kinds Fc Fa (34). Hypothetical effects of tho granitic movements in Cornwall (35). Numerical predominance of lodes (Fc) which dip in the same direction as the strata (37). ■General Characters of the Rocks and Lodes of Cornwall (37). Distinction between mine granite and quarry granite (38). Different kinds of killas (39). Mining districts in Cornwall and Devon (41). East and west systems which have fractured the ground in Cornwall ; E.W. (magnetic) direction of the principal lodes, and of the great metalliferous zone extending from Cape Cornwall to near Exeter (44) . Directions of the lead-bearing cross-courses (46). Resume ; rocks non-homogeneous, consisting of beds of unequal resistance, of considerable thickness, and but little inclined ; the mean underlie of the lodes (P=70 . greater than the dip of the strata (i=15° to 50°) ; angle (a) comprised between the strike of the country, and the bearing of the system of fracture often small ; dip of the normal rich parts often but little inclined beneath the horizon (47).

Comparison with the lead districts of Alston Moor (48), and Cardiganshire (51). . — East and West Lodes of Cornwall a. — Formation and opening of the fissures due to a descent of the hanging wall (55). Cross-section of the lode ; underlie (Pr) of the rich parts, (Pm) of the poor parts, (Pr — Pm) inflexions in cross-section (55). Formula e=h J_I__z_i_?) connecting the openings of the walls of the rich parts with the amount of fall of the hanging wall (56). ■Observed widths of lodes, mean width, examples of great variations in lodes of tin, copper, and lead (57). Totalisation of lodes (60), relative dimensions of the lode at Dolcoath (61) . ■Underlie or dip of a lode (P), and of its rich and poor parts (Pr and Pm), and the difference (Pr — Phi) (62). Calculated values of Pm from Appendix B (63).

Probable amount of faulting corresponding to openings of different widths (65). ■Condition of the walls during the descent of the hanging wall ; alteration of the walls, production of flucans, capel s (66); brecciated structure (67) ; feed.ers and droppers (68) ; branches, horses (69) ; circumstances which modify the openings by interrupting the flow of the mineral solutions ; local closing by partial descent of the hanging wall ; interruptions effected by cross-courses (70). -Influence of the relative and absolute thicknesses of the favorable and unfavorable strata and of the amount of fault (71). .— Characteristics of the Lodes Fc and Fa, in plan, longitudinal section and profile (73) ; deviations observable in the levels ; bearing of the normal plane C73) ; turns and warps (74) ; explanations of the diagrams illustrating two fissures Fc and Fa occurring in the same rock (74) • principal consequences of the difference of underlie (75) ; greater frequency of lodes Fc (76).

Table of Contents. IX a. — Changes in the underlie (P) of lodes (77) ; examples of inversion (78). 6. — Changes in the dip (i) of the rocks, subterranean ridges of granite (80). c. — Bad influence of contortions of strata (81) ; examples in the Gwinear District (82) V. — Sterile and Metalliferous Cross-courses generally straighter, more nearly vertical (83) ; wider than lodes ; flucans and cross-courses properly so-called (84) ; cross-course spar indicates poverty in the metalliferous waters ; ground in neighbourhood often disordered (85). a. — Circumstances under which cross-courses appear to have been formed, predominating directions (86). 6. — Examples of metalliferous cross-courses, Restormel (88) ; Trelawney, Huel Mary Ann, and Herodsfoot (89) ; distribution of the mineral in the lodes (91).

VI. — Influence of Parallelism ; vis-a-vis of riches (92) ; its application to lateral branches (93), and to the lodes of Camborne and Illogan (94) ; four zones of mines in that district (96) ; lines perpendicular to these zones caunter lodes (99) ; complex fissuring in this district (101) ; predominating influence of the systems of Finistere and Westmoreland (101). CONCLUSION. A knowledge of the systems of upheaval and of fracture in a mining district useful to the miner (103) ; influence of the Pays Bas system during the permian epoch (10-4) ; application of the progress of stratigraphy (106) ; advantages of Cornwall as a field for studying the phenomena of metalliferous deposits (106). AFFENDIX. Note A. — Explanations of terms used by M. Elie de Beaumont (107). 1. — Mountain Ststems their relative ages (108) ; their parallelism (109), provisional great circles of comparison (110), and extent (111) ; transport of their directions to any given point (111). 2. — The Pentagonal Network (Roseau Pentagonal) (112) .

Localization of the reseau on the earth's surface (116). Stratigraphic Systems (117). Note B. — Calculations of bearing, and dip of a given fracture under specified conditions (119). Note C. — Mode of constructing the diagrams illustrating the lodes of Fc and Fa (127). Note D. — Numerical statements as to the eleven ancient systems observable in Cornwall. Values of the angular deviations which are met with (133). Note E. — Observations on bearings and directions. The compass graduated into octants (142). Plates and descriptions. Table of Contents. CONTENTS OF THE ELATES PI. I, illustrating Chap. 1. Form of the rich parts. Examples of the principal types. Figs. 1 and 2. Course of Ore at Huel Seton. Fig. 3 Bunches in the crown's lode at Botallack Mine. Fig. 4. Shoots at Snailbeach. Fig. 5. Section of a rich lode at Alston Moor.

PI. II. Diagrams illustrating Chap. 1 Characteristics and surroundings (allures) of the lodes, and of the normal rich parts. Fig. 1. Variations in underlie ; steepness of the rich parts. Fig. 2 and 3. Variations in direction ; mean direction Fig. 4. Great inflexions. Fig. 5. Horizontal projection or plan of successive and equidistant levels in two rich parts. Figs. 6, 7 and 8. Lodes Fc Fa. The four general characters absolute for the normal rich parts. PI. III. Diagrams illustrating Chap. II. Formation of fissures and openings. Fig. 1. Granitic movements in Cornwall at two periods. Figs. 2 to 5. Branches on the hanging and foot walls. Figs. 6 and 7. Great lateral branch forming a horse. PI. IV. Geometric constructions illustrating Chap. II. Figs. 1 and 2. Relations between the underlie (Pr) of the rich part, (Pm) of the poor parts, the separation of the walls, and the amount of fault.

Fig. 3. Diagram of the flutings (cannelures) of a lode Fc. Fig. 4. Analagous figure for a lode Fa. Fig. 5. Section of lodes Fc and Fa by a plane perpendicular to the beds of the " country." Fig. 6. Horizontal section of the same lodes indicating their mean direction. Fig. 7. Mean underlie of each lode. PI V. Diagrams illustrating Chap. II, of the comparative allures of lodes Fc and Fa, of which the initial fractures are due to the same systems. (See also Note C). Figs. 1 and 5. Plans based upon and illustrating figs 3 to 7, PI. IV. Figs. 2 and 6. Sections perpendicular to the mean planes of the lodes Fc Fa. Figs. 3 and 7. Vertical projections parallel to the mean directions of the lodes Fc Fa. Figs, i and 8. Plans of several equidistant levelB. Contents of the Plates. XII Pi PI. Pi VI Lodes and cross-courses of the Camborne district.

Sketch of the principal lodes of the tin and copper mines situated on tho flanks of Carn Brea. VII. Illustrating Notes B, C, and D. Fig. 1. Direction and dip of the normal plane. Note B. Fig. 2. Apparent coincidences of deviated directions. Note D. Figs. 3 and 4. Compass graduated into octants for more convenient reading of directions. Note E. VIII. Illustrating Note A. Fig. 1. Parallel great circles. Fig. 2. Parallel chains. Fig. 3. Positions of the points A and M. Fig. 4. Transport of M to any given point. Figs. 5 to 10. The Pentagonal Network (IUseau). Plate !. Fate H. Plate Iff. __ .£ _* Z ./rtf , T#U#0- Plate IV. L**l I tilt '**** Plate v. Plate VI rm>cHomn Hate "VOI. . . UMS&lAÆ^ mo Plate VIII. ■A/re & iAJCÆtirr# r/?(//ri

INTRODUCTION.

. THE mineral riches of lodes are almost always very unequally distributed, and the workings afford evidence of sterile zones, as well as of others which are productive in differ ent degrees. In most of the lodes the rich parts constitute, so to speak, a series of " mines within the mine;" and it is naturally upon these parts that the work of "exploitation" is concentrated, whereas the "poor" parts are simply cut through by the neces sary galleries of communication. The form and relative position of these rich parts correspond pretty accurately with the places from whence most of the min eral is broken. As the geometric projection of these excavations presents a kind of outline of the masses removed, if the works have been well conducted, the traces thus obtained differ but little from the natural limits of the rich parts.

If the situation and configuration of these rich parts could be foreseen, the exploitation of metalliferous lodes would lose its hap hazard character, and the engineer would be enabled to devote his whole attention, as in other industries, to the economic con ditions and technical proceedings most suited to each particular case. The miners — turning tradition to account — proceeding by analogy and comparison, try to overcome chance; and by conjec tures based upon experience — making use of the smallest indica tions by most remarkable foresight — often ascertain the general conditions of the deposit {gite). A Introduction. For the observant miner the phenomena to be seen in the lodes are so numerous that each one opened by his labours im prints on his memory some particular recollection, while their peculiarities give to each a kind of individuality.

The same re mark applies to general facts : each mining district has its own character ; each group of districts or mining country is distinct from all others from the point of view with which we are concerned, viz., the peculiarities of the rich parts. These variations result mainly from a fact universally recognized, viz., that the general character of the veins, and consequently their riches, depend upon the nature of the containing rocks. This common fact results from the common mode of origin of the lodes. The rocks have been fractured, so producing subterranean channels for the circulation of mineral waters. The rocks have, therefore, been subjected unequally, and with a varying intensity, during one or more geological periods, to the action of those physical and chemical forces which have determined their mineral contents.

To take some examples from England. The lodes of tin, cop per, and lead in Cornwall and Devon traverse primary schists ; those of tin and copper also penetrate the granite, elvan ("quartz porphyry"), and greenstones ("hornblendic rocks"). The lead mines of Wales (Cardiganshire, &c.) are in silurian schists, far from eruptive rocks, while the lodes of galena in the North of England occur in carboniferous strata. In each of these countries metalliferous zones or regions may be distinguished where the strata or beds are productive, and the rocks favourable for mineral.* The disposition of the lead lodes of the Mountain Limestone in steps (" gradins") is well-known. This formation includes beds of limestone and of quartzose sandstones, alternating with argillaceous schists, which are but little inclined.

The hard lime stones and sandstones ("firestone") have been fractured almost vertically, and these contain the mineral riches ; whilst in the schist the lodes are reduced to the state of thin veins, or flat and sterile fissures. To these lodes the pipe veins and flats are attached ; *Such expressions aa 5.00c? channel of ground, mining zone, suitable strata, bearing ground, kindly, SfC, are used to qualify the terms Mllas, granite, or elivan. Introduction. 3 these are accessory deposits occurring in some of the limestone beds. The mechanical and chemical actions in these lodes are distinctly appreciable although superposed. When the lode passes through silicious rocks the walls are but little corroded, but in the limestones the chemical action of the circulating waters upon the walls is largely associated with the force of gravity, and has been able to contribute greatly to the formation of the cavity.

In all mining countries, wherever calcareous strata are met with, we are at once convinced of their great influence upon the general character of the lodes, but in formations consisting entirely of schistose rocks it is only by the most minute observation that we are able to distinguish practically between the good and bad strata. Still, in the silurian schists of Cardiganshire the miner does not fail to distinguish the favourable strata by their physical charac ters ; he prefers compact schists of moderate hardness, but dis likes the very soft argillaceous schists ("mudstones") and the fissile schists passing into slate. In these veins of galena, as in those of the Mountain Lime stone, the mechanical action of gravity has predominated in the formation of the cavities, i.e., the configuration of the rich parts, but here it is more difficult to recognize the effects of chemical action upon the walls.

In Cornwall and Devon some of the lodes are entirely in schist, others entirely in granite, while others again cut through both these rocks, and often the elvans and greenstones also. To this variety of enclosing rock* is added that of the minerals and veinstones. Notwithstanding the absence of calcareous beds, chemical action is evident in the lodes ; it is powerfully developed in a great many places, and notably in those stanniferous deposits which abound in tourmaline. f Nevertheless, the fractures and relative displacements of the encasing rocks do not cease to be discernable, and in spite of the complexity of the phenomena we may follow in the lodes of the two counties, very clearly, the di rections of the " stratigraphic systems " to which they belong. * " Country." t " Schorl " or " cockle," are the Cornish miners terms for black tourmaline.

Introduction. 4 Without losing sight of the action of chemical forces upon the " country," we shall avail ourselves of the force of gravity, which is not masked, and we shall seek in the physical properties of the rocks the first cause of the configuration of the rich parts. In selecting Cornwall as a field of study, I would recall the opinion expressed by Mr. R. W. Pox in his excellent memoir " On Mineral Veins."* " I believe it will be found, on investi gation, that the mineral veins of Cornwall differ very little from those which have been observed in other mining districts in what may be termed their mechanical characters. "t The works of English geologists treating of Cornwall and Devon are both numerous and varied ; they embrace, collectively and in detail, the two sides of the subject, General Geology and Metalliferous Deposits.

It will be sufficient to mention here : — The Transactions and Annual Reports of the Royal Geological Society of Cornwall. The fine work of Sir H. De la Beche, " Eeport on the Geology of Cornwall, Devon, and West Somerset, 1839," and, by the same author, the memoir ' ' On the formation of the rocks of South Wales and South Western England, 1846." Different memoirs by Sir R. Murchison. J. Carne, " On the Relative Age of the Veins of Cornwall, 1822." R. W. Fox, " On Mineral Veins, 1836.' W. J. Hen woods "Metalliferous Deposits of Cornwall and Devon, 1843." Two volumes " On Metalliferous Deposits and on Subterranean Temperature," published in 1871, by Mr. Henwood, which refer to mines situated in Cornwall, as well as in different parts of the globe. I would mention, also, Mr. Charles Thomas's interesting " Remarks on the Geology of Cornwall and Devon, in connexion with the deposits of metallic ores, and on the bearings of pro ductive lodes," published in 1859 ; also the very able descriptions of mines given by Mr. H. C. Salmon in the Mining Journal, and in 1862-4, in the Mining and Smelting Magazine. * Report of the Royal Cornwall Polytechnic Society, 1836, pp. 81 — 141. + Ibid., p. 96.

Introduction. 5 In 1862 I presented, in the succint form of conclusions, the principal results which I believed I could draw from the application of the directions of the Stratigraphic Systems^ to the study of general geology, and of the deposits of Cornwall. I hoped then to have been able to develope the evidence of these statements in a series of memoirs, shewing, in the first place, the influence of the eleven most ancient systems upon the general mass of Cornwall and Devon ; in a second work to examine each of the more important metalliferous districts ; and finally, to complete the practical object of these researches by pointing out how the miner might apply these ideas, which are less abstract than one might suppose, to the working of the veins. In 1865 I had drawn up a good part of the first memoir, and laid down pretty carefully the lines of direction upon the map of Cornwall, but since then a variety of circumstances have obliged me to suspend my project, and induced me to present at first such partial results of my studies as seem to me more directly useful to the miner.

I shall rely upon the observations which I was able to make in Cornwall at different times between the years 1855 and 1866, and I shall draw abundantly upon the English works already mentioned, and especially those of Mr. W. J. Henwood. This presents an immense collection of personal observations, together with the fruits of a vast erudition. In bringing together these rich materials the author has treated them with the most scrupu lous reserve. In his ' ' Address delivered as President of the Royal Institution of Cornwall," in 1871, he summarized his ob servations on metalliferous deposits, and in spite of his modest denial he has contributed some general rules of inestimable value for the guidance of the miner.* The present work consists of two chapters ; in the first I describe the different forms of the rich parts, and indicate the general characters of those parts, and I conclude by shewing their mutual connection with each other. % See appendix A. * The geological portion of this address was published in the " Report of the Miners' Association of Cornwall and Devon for 1872."

J. H. C. Introduction. In the second chapter, making use of hypothesis, I apply the conclusions of the first chapter to the study of the subterranean channels produced by the fracture and movements of the ground. In a resume, taking the lodes of Cornwall for example, my aim is to shew how the knowledge of the directions of the Stratigra phic Systems may be made useful to the miner, and how that knowledge may be acquired by a series of observations properly made underground.

Chapter I

1. — Riches and Poverty in the lodes. MOST of the metalliferous veins present, as is well-known, very great variations of riches in their different parts. In one place the lode is sterile through the entire absence of useful minerals ; in another it is unproductive, because the proportion of such minerals is not sufficient to pay cost, elsewhere the lode is called productive or rich, at such places as, all expenses being paid, its exploitation leaves a more or less considerable profit. It is evident that these terms depend principally upon pecu niary conditions and results, varying much in the same lode with the conditions of labor and the market value of the mineral, but at any given moment, and under specified modes of working, the miner is enabled by his experience to apply these epithets pretty accurately.

One type of riches is a " strong" lode containing mineral of a massive or at least a well-marked character. These conditions are often accompanied by a vein-stuff of moderate hardness, and a considerable stability in the "walls" of the lode so that the labor of the miner is lessened, and the expenses of " breaking," "tramming," and " dressing," are reduced to a minimum. The elements of poverty on the contrary are, a lode thin and hard, and often subdivided into threads. The " country," also, is hard and troublesome for drivage ; or else, on the contrary, both vein and country are too soft, and therefore fall together. The vein may not perhaps be really small, taking into account its numerous branches, but the mineral is so disseminated through the earthy matter of the vein-stone in little spots or threads, that the expenses of "breaking," "timbering," and " stulling" swallow up all the profit.