Notices of Memoirs — Classification of Ore-deioosits. 223 

 isroTiCES OF ]vi:b:m:oi:rs. 



A New Classification of Oke-deposits. By Dr. F. H. Hatch. 



IN his presidential address to the Institution of Mining and 

 Metallurgy,' Dr. F. H. Hatch gave the following outline of 

 a new classification of ore-deposits : — 



Modern views on ore-genesis may be reduced to two principal lines 

 of inquiry, the one dealing with the agent or vehicle, by which the 

 metals have been collected, conveyed to, and deposited in the places 

 where they are now found, and the other with the nature of tlie 

 concentrates formed in the course of these processes. 



Considering the latter first, ore-deposits are found to be either — 



1. Igneous differentiates. 



2. Cavity-fillings. 



3. Metasomatic replacements. 



4. Stratified or sedimentary deposits. 



5. Residual deposits. 



Of these, the sedimentary deposits comprise marine, lacustrine, and 

 fluviatile accumulations, including placers. 



Coming now to the agent or vehicle of ore-coLcentratiou, these 

 are found to be — 



(a) Molten magmas. 



{h) Gases and vapours above their critical temperatures. 



(c) Deep-seated waters, whether of magmatic or of meteoric origin. 



{d) Vadose waters. 



(e) Chemical and bacterial agents in lakes and seas. 



(/) Mechanical agents, such as moving water and wind. 



It is possible, by combining the facts elicited by these two lines 

 of inquiry, to formulate a genetic scheme of classification. For 

 example, cavity-filling may be due to igneous injection, to gases and 

 vapours above their critical temperatures, to deep-seated waters, 

 or to vadose waters ; again, metasomatic replacement may be brought 

 about by gases and vapours, by deep-seated waters, or by vadose 

 waters. By arranging these two series of relationships in vertical 

 and horizontal columns respectively, all the various types of ore- 

 deposits are obtained at their intersections ; and in this way the 

 classification shown in the accompanying Table (pp. 224-5) is obtained. 



" Considering the world-wide interest of England in the mining of 

 precious metals throughout the world, it seems rather singular that 

 so little attention is being given to ore-deposits by the geologists and 

 engineers of that country. It is true that there are notable exceptions 

 to this, but with English mining engineers working in the most 

 remote parts of the world it seems as if their contributions to the 

 science of ore-deposits is disproportionately small." - 



' Delivered at the annual meeting of the Institution held at Burlington 

 House on March 26. 



^ Lindgren, " Tendencies in the Study of Ore-deposits " : Econ. GeoL, vol. ii, 

 p. 745, 1907. 



