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Magnetite crystals with a cubic habit are rare but have been found at Balmat, St. Lawrence County, New York, [47] [48] and at Långban, Sweden. [49] This habit may be a result of crystallization in the presence of cations such as zinc. [50] Magnetite can also be found in fossils due to biomineralization and are referred to as magnetofossils. [51]
The process by which lodestone is created has long been an open question in geology. Only a small amount of the magnetite on the Earth is found magnetized as lodestone. Ordinary magnetite is attracted to a magnetic field as iron and steel are, but does not tend to become magnetized itself; it has too low a magnetic coercivity.
It is often found in association with volcanic or basaltic sands. For example, it is found in Tenerife, Spain, where the magnetite grains contain a very high amount of titanium and other impurities. The typical composition is 79.2% iron oxide, 14.6% titanium dioxide, 1.6% manganese oxide, 0.8% silica and aluminum oxide, and trace amounts of ...
The lengthy epidemiological study of Minnesota iron miners concluded in December 2014 that those working 30 years in the iron mines and living to be 80 years old had a lifetime chance of having a mesothelioma of 3.33 cases per thousand such workers, more than double the background rate of 1.44 cases per thousand people living to 80 years old.
The ore body at Benson Mine is composed of magnetite and non-magnetite ore. The average percentage of iron in both magnetite and non-magnetite ore was about 23%, less than the 40% at Chateauguay. Iron-ore deposits that contained 50% or more iron were depleted in the United States by the mid-1940s.
Created Date: 8/30/2012 4:52:52 PM
John Sinkankas (May 15, 1915 – May 17, 2002) was a Navy officer and aviator, gemologist, gem carver and gem faceter, author of many books and articles on minerals and gemstones, and a bookseller and bibliographer of rare books.
Magnetofossils are the fossil remains of magnetic particles produced by magnetotactic bacteria (magnetobacteria) and preserved in the geologic record. The oldest definitive magnetofossils formed of the mineral magnetite come from the Cretaceous chalk beds of southern England, while magnetofossil reports, not considered to be robust, extend on Earth to the 1.9-billion-year-old Gunflint Chert ...