Bevieius — Mineral Resources of Great Britain. 39 



associated with fluorspar and galena, and is probably due to heated 

 vapours and solutions derived from igneous magmas. 



It is shown that the total reserves in the localities described are 

 insignificant, amounting to j^erhaps 750,000 tons, as compared with 

 a possible 135 million tons in Cumberland and Lancashire ; neverthe- 

 less, some of these ores are of good quality, and may eventually 

 become valuable for special purposes. It may be mentioned that the 

 haematites of the Forest of Dean and South Wales, which are on 

 a much larger scale, are described in a separate volume. 



Special Eepop.ts on thk Mineral Resources op Great 

 Britain. Vol. X, Iron Ores (cont.) : The H.^imatites of 

 THE Forest op Dean and South Wales. By T. Franklin 

 SiBLY, D.Sc. Mem. Geol. Surv. pp. 92, with 14 figs. 1919. 

 Price 4s. net. 



TF direct evidence were required of the value to industry of the 

 -^ Geological Survey, none could be more convincing than the 

 series of Special Reports on the Mineral Resources of Great Britain 

 which have been produced during the War. They will appeal to 

 a different and perhaps more j)ractical public than do the Geological 

 Memoirs ; but on the other hand it is clear that the high standard 

 of these jDractical reports could not have been attained without the 

 purely geological researches i^reviously made by the Survey. The 

 present monograph is a welcome addition to the literature of iron- 

 ores. Dr. Sibly describes the features of the haematite deposits in 

 the Carboniferous Limestone briefly and lucidly. The explanation of 

 the origin of the haematite bodies should be of interest to students 

 of economic geology, as the theory of the metasomatic replacement 

 of the limestone by iron-ore from ferruginous solutions derived from 

 the Trias is satisfying and provides a good exam2)le for instructional 

 purposes. If there is any genetic connexion between the ore bodies 

 and the other metasomatic replacement of the limestone by dolomite 

 it is obscure and left unsettled, though there is evidence that 

 dolomite was formed at three periods, so that it is necessary to 

 distinguish between primary dolomite and contemporaneous and 

 subsequent dolomitization. The greater portion of the report deals 

 with accounts of the mines, both working and abandoned. 

 Statistics of output in the past and also estimates of the amount of 

 iron-ore remaining (so-called " reserves ") are given, though the 

 author sees no hope for the resuscitation of the mines under present 

 conditions. 



