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Lodestones are naturally magnetization pieces of the mineral magnetite. They are naturally occurring , which can attract iron. The property of magnetism was first discovered in Ancient history through lodestones. Pieces of lodestone, suspended so they could turn, were the first , and their importance to early navigation is indicated by the name lodestone, which in Middle English means "course stone" or "leading stone", from the now-obsolete meaning of lode as "journey, way".: 'Literally 'way-stone', from the use of the magnet in guiding mariners.'
Lodestone is one of only a very few minerals that is found naturally magnetized. Magnetite is black or brownish-black with a black streak, with a metallic luster and a Mohs hardness of 5.5–6.5.
The other question is how lodestones get . The Earth's magnetic field at 0.5 gauss is too weak to magnetize a lodestone by itself. The leading theory is that lodestones are magnetized by the strong magnetic fields surrounding lightning bolts. This is supported by the observation that they are mostly found near the surface of the Earth, rather than buried at great depth.
The earliest Chinese literary reference to magnetism occurs in the 4th-century BC Book of the Devil Valley Master ( Guiguzi).The section "Fanying 2" (反應第二) of The Guiguzi: "其察言也，不失若磁石之取鍼，舌之取燔骨".
In the chronicle Lüshi Chunqiu, from the 2nd century BC, it is explicitly stated that "the lodestone makes iron come or it attracts it."
From the section " Jingtong" (精通) of the "Almanac of the Last Autumn Month" (季秋紀): "慈石召鐵，或引之也]" The earliest mention of a needle's attraction appears in a work composed between 20 and 100 AD, the Lunheng ( Balanced Inquiries): "A lodestone attracts a needle."In the section " A Last Word on Dragons" (亂龍篇 Luanlong) of the Lunheng: "Amber takes up straws, and a load-stone attracts needles" (頓牟掇芥，磁石引針). In the 2nd century BC, Chinese Geomancy were experimenting with the magnetic properties of lodestone to make a "south-pointing spoon" for divination. When it is placed on a smooth bronze plate, the spoon would invariably rotate to a north–south axis. While this has been shown to work, archaeologists have yet to discover an actual spoon made of magnetite in a Han tomb.Joseph Needham, Clerks and Craftsmen in China and the West: Lectures and Addresses on the History of Science and Technology. Cambridge: University Press, 1970, p. 241.
Based on his discovery of an Olmec artifact (a shaped and grooved magnetic bar) in North America, astronomer John Carlson suggests that lodestone may have been used by the Olmec more than a thousand years prior to the Chinese discovery. Carlson speculates that the Olmecs, for astrological or geomancy purposes, used similar artifacts as a directional device, or to orient their temples, the dwellings of the living, or the interments of the dead. Detailed analysis of the Olmec artifact revealed that the "bar" was composed of hematite with titanium lamellae of Fe2–xTixO3 that accounted for the anomalous remanent magnetism of the artifact. Evans, B. J., Magnetism and Archaeology: Magnetic Oxides in the First American Civilization, p. 1097, Elsevier, Physica B+C 86-88 (1977), S. 1091-1099
"A century of research has pushed back the first mention of the magnetic compass in Europe to Alexander Neckam about +1190, followed soon afterwards by Guyot de Provins in +1205 and Jacques de Vitry in +1269. All other European claims have been excluded by detailed study..."Needham, Clerks and Craftsmen, p. 240.
Lodestones have frequently been displayed as valuable or prestigious objects. The Ashmolean Museum in Oxford contains a lodestone adorned with a gilt coronet that was donated by Mary Cavendish in 1756, possibly to secure her husband's appointment as Chancellor of Oxford University. Isaac Newton's signet ring reportedly contained a lodestone which was capable of lifting more than 200 times its own weight. And in 17th century London, the Royal Society displayed a spherical lodestone (a terrella or 'little Earth'), which was used to illustrate the Earth's magnetic fields and the function of mariners' compasses. One contemporary writer, the satirist Ned Ward, noted how the terrella "made a paper of Steel Filings prick up themselves one upon the back of another, that they stood pointing like the Bristles of a Hedge-Hog; and gave such Life and Merriment to a Parcel of Needles, that they danc'd ... as if the devil were in them."
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