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429 



THURSDAY, JANUARY i, 1920. 



BRITISH IRON ORES. 

 Special Reports on the Mineral Resources of 

 Great Britain. Vol. viii., Iron Ores : Haematites 

 of West Cumberland, Lancashire, and the 

 Lake District. By Bernard Smith. Vol. ix., 

 Iron Ores (continued) : Sundry Lnbedded Ores 

 of Durham, East Cumberland, North Wales, 

 Derbyshire, the Isle of Man, Bristol District 

 and Somerset, Devon and Cornwall. By T. C. 

 Cantrill, Dr. R. L. Sherlock, and Henry Dewey. 

 Vol. X., Iron Ores (continued): The Haematites 

 of the Forest of Dean and South ]]'ales. By 

 Prof. T. Franklin Sibly. (Southampton : Ord- 

 nance Survey Office, 1919.) Trices: \ol. viii., 

 9-s. net; vol. ix., 3.';. 6d. net; vol. x., 4.S. net. 



AS is well known, one of the effects of the 

 recent war has been to direct the attention 

 of the British people to the wealth of the 

 mineral resources of their own country, whereupon 

 it soon became apparent that accurate official in- 

 formation as to the nature and extent of 

 these resources was conspicuous only by its 

 absence. Fortunately, the Director of the 

 Geological Survey, Sir .\ubrey Strahan, took 

 immediate steps to rectify this deficiency, and a 

 series of volumes on the mineral resources of 

 Great Britain has been issued under his direc- 

 tion ; the last three of these have just been 

 published. These are the opening volumes of a 

 set dealing with British iron ores, and Sir Aubrey 

 Strahan has written a short preface to the first 

 of them, in which he indicates the general scheme 

 which it is proposed to follow. He divides the 

 British ores into "three classes, namely, those pro- 

 ducts, mostly haematites, which occur as replace- 

 ments, in lodes, etc. ; the bedded ores of iMesozoic 

 age; and the bedded ores of Palaeozoic age." 



This classification is a quite satisfactory one, 

 though the use of the word " lodes " in the above 

 description may well be objected to if it is in- 

 tended to imply that replacements and lodes are 

 equivalent terms. A typical replacement de- 

 posit is certainly not a typical lode ; the 

 latter term is identical in meaning with vein, 

 and ought to be restricted definitely to mineral 

 deposits filling fissures, which show for the most 

 part well-defined walls, and have a fairly regular 

 form, so much so that authorities like, e.g., Sir 

 Clement Le Neve I"o.ster, have, made them a sub- 

 division of the tabular or sheet-like deposits. It 

 is quite true that the walls of a lode generally 

 show more or less alteration due to the same 

 NO. 2618, VOL. 104] 



causes that brought about the filling of the 

 lode itself, and that this alteration may take the 

 form of impregnation or of mora or less complete 

 replacement of the country rock, but this fact does 

 not justify calling the lode a replacement deposit. 

 The typical replacement deposit, on the other 

 hand, is, as a rule, quite irregular in outline, and 

 if it does at times assume a tabular form, this 

 is due to accidental conditions, and is certainly 

 not a genetic characteristic. 



The three volumes now issued cover the 

 first of Sir Aubrey Strahan's classes, and form 

 geologically the most interesting, but economically 

 the least important, of the three ; in fact, it is 

 only the ores described in vol. viii. that possess 

 any economic importance whatever. As regards 

 the economic aspect, it may be considered un- 

 fortunate that the authors of the three volumes 

 have put forward statements as to what they 

 consider the probable ore reserves contained in 

 the mineral fields that they have investigated. In 

 the case of irregular deposits, such as are here 

 dealt with, this is a problem of exceptional diffi- 

 culty, seeing that the data for its solution do not 

 exist, and sound estimates of quantity are impos'- 

 sible ; the best that can be done is to make a 

 more or less intelligent guess, and under these 

 conditions the best possible guess is likely to be 

 very wide of the mark. Such speculations are 

 somewhat out of place in an authoritative Govern- 

 ment publication, and it is greatly to be feared 

 that heavy money losses may be incurred by ad- 

 venturers who dt) not discriminate between the 

 geologist's idea of the quarytity of ore that may 

 be supposed to exist and the miner's view of the 

 amount that can be economically extracted. 



Apart from his attempt at estimating the prob- 

 able ore reserves, Mr. Bernard Smith's volume on 

 the West Coast hfematites is in every respect a 

 very satisfactory one ; here the difficulty of form- 

 ing any opinion as to quantity is peculiarly strik- 

 ing. Owing to the soft nature of the ore and to 

 its highly irregular mode of occurrence, ore re- 

 serves cannot be blocked out for any length of 

 time in advance, and there is rarely, if ever, any 

 "ore in sight" in the accepted sense of that 

 phrase, although mines have continueti for many 

 years, and will doubtlessly continue ir the future, 

 to produce considerable quantities of ore by the 

 hand-to-mouth methods of exploitation which the 

 nature of the deposits renders necessary in the 

 great majority of cases. The volume gi\es a 

 short but sufficient and very clear description of 

 the geology of the district, and the mode of 

 formation of the ore bodies is de«icribed in very 

 convincing terms. It seems impossible to doubt 



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