34 Revieios — J. Arthur Phillips' Ore- Deposits. 



III. — A Treatise on Ore Deposits. By John Arthur Phillips, 

 F.R.S., V.P.G.S., F.C.S., etc. Royal 8vo. pp. 652, and xvi. with 

 95 Illustrations. (London : Macmillan & Co., 1884.) 



ME. PHILLIPS is well known as a high authority on all matters 

 relating to Mining and Metallurgy ; his " Manual of Metal- 

 lurgy," and his "Mining and Metallurgy of Gold and Silver," 

 being standard books of reference. 



In the present work the author has been assisted by Mr. B. PL 

 Brough, A.R.S.M., and the illustrations are from the pencil of Mr. 

 Frank Rutley. The subject is treated in the broadest and most 

 cosmopolitan manner, every country in which mining operations are 

 carried on being more or less fully noticed. Commencing with 

 Ore-deposits in general, the author writes : — "Metals which occur in 

 a state of approximate purity are said to be native, and when two or 

 more such metals are found in combination, the mixture is called a 

 native alloy. Usually the metals sought after by the miner are, 

 however, not found in the native state, but are mineralized by 

 uniting with various non-metallic bodies. In this way they combine 

 with sulphur or chlorine, giving rise, respectively, to metallic sul- 

 phides or chlorides ; with oxygen the metals form oxides, and with 

 acids they yield salts, such as carbonates, sulphates, and phosphates. 



" All natural combinations of a metal with such mineralizing sub- 

 stances are called ores when the proportion of metal which they 

 contain, after suitable mechanical preparation, is sufficiently large to 

 admit of their being advantageously treated by the metallurgist. 

 Although perhaps not strictly correct, any material obtained by 

 mining that contains a workable proportion of a metal is often called 

 an ore, even if the whole of the metal be present in the native state. 



Ores of the different metals are sometimes found in surface-deposits, 

 disseminated through igneous and sedimentary rocks, in more or less 

 regularly stratified or bedded formations, in detached masses, and, 

 above all, in veins of various descriptions. The non-metalliferous 

 minerals forming part of the latter are known as the matrix, gangne, 

 or veinstone. Metalliferous minerals are found in rocks of every 

 geological age ; but they occur most frequently in mountainous 

 districts, and in the older rocks, especially near junctions of igneous 

 rocks with those of sedimentary origin. They are also frequently 

 met with in strata which have either been penetrated by eruptive 

 dykes, or have been subjected to extensive metamorphic alteration. 

 The ores of each of the different metals are, however, often restricted 

 within certain geological horizons, beyond which they seldom occur 

 in remunerative quantities. 



" Gold, platinum, and tin ore are found in alluvial detritus, in which 

 they evidently were not formed by chemical action, but result from 

 the disintegration of older deposits whose constituents have been 

 removed and re-arranged by the mechanical agency of water. 



" The fragments constituting the superficial deposits are usually 

 much water- worn, and the associated metals or metalliferous particles 

 are mainly concentrated in particular areas, over which water has 

 flowed with great activity. Metalliferous deposits of this kind are 



