Identification of magnetic minerals in rocks Rocks are assemblages of diamagnetic, paramagnetic, and ferrimagnetic minerals. Concentration of ferrimagnetic minerals is usually very small (< 1 %) Microphotograph of a thin section of norite dolomite limestone sandstone shale Sedimentary rocks Volcanic rocks granite gabbro basalt 1 10 -1 10 -2 10 -3 10 -4 10 -5 Magnetic susceptibility, κ (SI units) Median values and ranges of the magnetic susceptibility in common rock types Modified from Lowrie, 1997
Magnetic Field of Other Planets Mercury – yes, but weak Venus – no, or very weak Mars – no clear evidence for field, but might have had field in the past Jupiter – yes, very strong (20,000 times earth) Saturn – yes 500 times earth Uranus – yes, strong tilt with respect to rotational axis
Source: NASA http://photojournal.jpl.nasa.gov/jpeg/PIA02008.jpg
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