Revieu-s—Tin Ores, 1919. 179 



Tin Ores, 1919. Monographs on Mineral Eesources. By 

 G. M. Davies. pp. 111. Imperial Institute. 3s. %d. net. 



THIS monograph is one of a series which is being issued by the 

 Mineral Resources Committee of the Imperial Institute. It 

 is only in recent years that geologists have taken more than a 

 passing interest in economic geology, but with the increased attention 

 paid to it by eminent scientists the subject has assumed an academic 

 importance not hitherto known, and one may recall the early days 

 when it was treated as a mere accessory to mining instruction. 

 The result is that the literature of mineral economics has improved, 

 and this monograph is an excellent example of the way in which 

 such a monograph should be jDrepared. It maintains a just balance 

 of treatment between the statistical and scientific aspects, a feature 

 often lacking in economic papers. On the whole this monograph is 

 rather more economic than geological, and in this we discern that 

 there is a difference between "mineral resources " and " economic 

 geology ". 



Although the occurrences of tin ore in the British Empire receive 

 the chief attention, the foreign statistics and geology are adequately 

 dealt with, while the exports and imports of different countries 

 give an excellent idea of the tin trade as a whole. Some of the 

 information is of transient interest only and need hardly have been 

 embodied, e.g. the price of metallic tin in London. 



To English geologists the most interesting original contribution 

 is that of Professor Cronshaw, who describes the structures of the 

 Cornish and Devon lodes at various places, and we quote a passage 

 relating to the lodes of Camborne. " The mineral contents show a 

 definite arrangement within the lode fissures, and, moreover, display 

 well-defined mutual relationships. This definite arrangement is 

 the outcome of a definite order of intrusion, which, for the Camborne 

 district — and it very probably admits of a wider application — has 

 been found to be as follows : — 



I. Large-grained and considerably brecciated quartz. 

 II. Small-grained quartz, cassiterite, tourmaline, and chlorite. 



III. (a) Brown, finely crystallized tourmaline and chlorite, or 

 ' brown peach ' with minute grains of cassiterite and a certain 

 amount of arsenopyrite. 



(&) ' Blue peach ' with cassiterite and some arsenopyrite. 



IV. {a) Fluorspar, and to a less extent, secondary quartz veins 

 containing a little copper pyrites and occasional recrystallized 

 cassiterite. 



(&) Calcite veins. 



(c) Veins of haematite, iron p3^rites, quartz, etc. 



[d) Veins of galena, zinc-blende, quartz, and copper pyrites. 

 The bulk of the cassiterite made its apj)earance in stage III {a)." 

 It is interesting to note that Professor Cronshaw confirms the 



view of apparent connexion between the cassiterite and the lead 

 ores, as a similar sequence of mineralization has frequently been 



