Abstract This brief section on mineral magnetism is meant to be a summary of the nature of the magnetic properties of minerals. A description of the nature of magnetism is given considering electron spin and orbital motion. Then a summary of the magnetic properties of naturally occurring minerals is given.

Abstract The magnetic characteristics of rocks are briefly discussed in this article. A discussion of the various factors affecting susceptibility has been included. A short description of various methods of measuring the magnetic properties of rocks is given and then an indication of the magnetic properties of some typical igneous rocks given. In general, basic intrusives and volcanics are found to have strong permanent magnetization which must be important in giving magnetic anomalies. Granitic intrusives, on the other hand, seem to have only weak and scattered remanent magnetizations so that the effect of sus-ceptibility is dominant. In many geophysical studies, it is found that the magnetic properties of rocks are of interest. It is usual to study both the susceptibility and the remanent magnetism of rocks. In the preceding section of this chapter, Cox and Doell have discussed the physical principles underlying remanent (or permanent) magnetization. In this section, discussions of magnetic susceptibility, of the measurement techniques used in studying the magnetic properties of rocksof the magnetic properties of various rock types are presented.

Abstract In this article a few typical applications of rock magnetism to the solution of geologic problems have been presented. These studies are limited to those where the magnetization probably acquired at the time of formation of the rock can be used as a correlation tool. In many rocks differing direction of permanent magnetization are seen to be useful. In rocks of widely differing age the results are probably the most useful. It also appears that sudden reversals of the earth's magnetic field can be useful as marker horizons. This is especially true in rocks of Tertiary and Quaternary age where the reversals have been the most thoroughly studied.

Abstract A series of model experiments has been carried out as an aid to the interpretation of horizontal-loop (Slingram) electromagnetic surveys. The model used was a large conducting sheet with various orientations subjected to various frequencies. It is shown how it is possible to derive the dip, depth, and conductivity-thickness product of such bodies. The interpretation procedure has been applied to a set of field data and it is concluded that the conductivity-thickness product is a useful parameter in the study of massive-sulfide deposits. These examples show that many sulfide conductors have conductivity- thickness products between one and 300, a surprisingly small range considering the possible range of values for conductivity and for thickness in natural deposits.