Chapter Iii. Some Salient Features of the Geology

AND CLASSIFICATION OF MINERAL DEPOSITS 29

VARIOUS METHODS OF CLASSIFICATION 29

NAMES 31

MINERAL DEPOSITS AS MAGMATIC SEGREGATIONS IN IGNEOUS ROCKS 34

MINERAL DEPOSITS WITHIN AND ADJACENT TO IGNEOUS ROCKS, WHICH WERE FORMED IMMEDIATELY AFTER THE COOLING AND CRYSTALLIZATION OF THE MAGMAS THROUGH THE AGENCY OF HOT MAGMATIC SOLUTIONS 36 Evidence of igneous source 37 Possible influence of meteoric waters in deposition of ores of this class 41 Zonal arrangement of minerals related to igneous rocks 42 The relation of contact metamorphism to ore bodies of the foregoing class 45

SECONDARY CONCENTRATION IN PLACE OF THE FOREGOING CLASSES OF MINERAL DEPOSITS THROUGH THE AGENCY OF SURFACE SOLUTIONS 46

RESIDUAL MINERAL DEPOSITS FORMED BY THE WEATHERING OF IGNEOUS ROCKS IN PLACE 50

MINERAL DEPOSITS FORMED DIRECTLY AS PLACERS AND SEDIMENTS 51 Mechanically deposited minerals 51 Chemically and organically deposited minerals 52

SEDIMENTARY MINERAL DEPOSITS WHICH HAVE REQUIRED FURTHER CONCENTRATION TO MAKE THEM COMMERCIALLY AVAILABLE 54

ANAMORPHISM OF MINERAL DEPOSITS 57

CONCLUSION 58