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Roger Weller, geology instructor

by Jonathan Barton
Physical Geology
Fall 2016

The Minerals of Magnets

Magnets come in many shapes, sizes, and strengths but few minerals make up their structure. Iron, nickel, and cobalt are the main elements, and when combined with some of the rare-earth elements they exhibit extraordinarily unique magnetic qualities.  When these metallic elements are melted into a conglomerate and subjected to an electromagnet to form a permanent magnet the combination is called a ferromagnetic, because iron (ferrum in Latin) is the most common and most abundant element of the mixtures.  Samarium and neodymium (to name a few) are rare-earth elements that make up the alloys of very strong magnets.  The rare-earth elements that are mixed with the one or two of the three main fundamental elementals are the key ingredients to fabricate very strong permanent magnets. These rare-earth magnets are in everything from mobile phones to electric cars.

Ferromagnetic elements display long-term magnetization at the atomic level. This is caused because the metals were heated to the curie point, where the unpaired electrons will line up parallel with each other with a little help from an electromagnet. That means before the minerals are heated up, the direction of the electrons are random. Each metal has its own perfect curie temperature.  After the metals are heated to the perfect curie temperature, for example iron is 1043K, the melted metal is put in an environment where there is a powerful electric magnet to line up the direction of the particles.  When the metals are in a raw sample, the minerals electrons will be unmagnetized and randomly orientated.  SEQ \* ARABIC 1


Ferromagnets will tend to stay magnetized to some extent after being subjected to the external magnetic field.  This tendency to "remember their magnetic history" is called hysteresis.  The portion of the magnetization which is retained when the magnetic field is removed is how elements are selected. When being chosen for production as permanent magnets how well they hold their magnetization is a large factor in the process.  All ferromagnets have a maximum temperature where the magnetic property disappears because of thermal distress.  Ferromagnetic materials will respond mechanically to an impressed magnetic field, changing length slightly in the direction of the applied field.  This property, called magnetostriction, leads to the familiar hum of transformers as they respond mechanically to 60 Hz AC voltages.

Rare-earth minerals of the Lanthanide family make super strong magnets because they require less energy to magnetize. Their electrons want to go in the same direction and resist being disorganized and becoming demagnetized.  Rare earth element is a broad term for many man-made minerals, and many of these are highly unstable and or toxic.  The term “rare” is not a correct term when describing these elements.  They are not rare at all.  They are in fact found all over the crust of our planet. The term “rare-earth” comes from the concentration of the element in the surrounding ore, 0.5 parts per million. When companies mine for rare earth elements there is more “trash” or tailings then there is of the actual material that they were looking for, 0.5 parts per million is what is classified as rare as far as mineral deposits go.  Most of these minerals are processed and mined in china due to their lack of environmental regulations; the waste or byproducts of refining of rare earth minerals is all toxic sludge that is either radioactive or hazardous to organic life.


            Samarium is a rare-earth mineral that when combined with the alloy known as cobalt, has the highest resistance to demagnetization known to any combination of elements.  The French chemist Paul Boisbandran found samarium in 1853 it was not until the 1970s that Samarium was used as a magnet. The discovery of these permanent magnets was by Albert Gale and Dilip K. Das of Raytheon Corporation. Samarium cobalt magnets are brittle and chip easily, the magnets are often coated with other metals to prevent damage to them while they are being used.  Samarium cobalt magnets are similar in strength to Neodymium magnets but have a higher curie point (1073K). They are used in place of neodymium when they need to use a magnet in high temperature environment. Samarium cobalt magnets are more expensive to make then Neodymium magnets and are not used extensively in everyday life.  SEQ \* ARABIC 1

Neodymium is the most widely used rare-earth mineral for permanent magnets and they are in everything from expensive electric devices to children’s toys. Neodymium magnets are inexpensive to manufacture because of their low curie point and their ability to remember their magnetic history with minimum magnetization required.  Neodymium iron and boron are the ingredients to create these super strong permanent magnets.  Neodymium magnets are so strong that they are dangerous if handled improperly and the largest ones can’t be shipped by regular mail.  The Neodymium element was discovered by German scientist Carl Auer von Welsbach in 1888 but wasn’t used as a magnet until 1982 by General Motors. The element allows us to miniaturize many electronic devices, the magnets are so strong it requires only a small amount of a magnet to make the device work.  SEQ \* ARABIC 1

Loadstone is the only natural occurring magnet on the whole planet, in the early days of human exploration we used it in compasses.  Human explorers, would never have discovered as much as they did, had they not used a compass made of loadstone. The first to use the loadstone in a compass was the Chinese.  Soon many famous explorers would use them to navigate the entire surface of the planet. Loadstone is made the same way as any other magnet, with an abundant source of heat and a magnetic field applied while it is being cooled. The first theories of how loadstone was naturally created was that the magnetic field of the planet slowly turned the piece of iron into a magnet over great periods of time. This hypothesis was disproven when a group of scientist from New Mexico Institute of Technology in Socorro, New Mexico hypnotized and proved lightening was in fact the creator of loadstone.  When lightning strikes a piece of magnetite it quickly heats the iron ore and deposits a magnetic charge to it.  SEQ \* ARABIC 1