Editing Lodestone

{{short description|Naturally magnetized mineral}}
{{for|a general description of the mineral itself|Magnetite}}
{{Other uses}}
[[Image:Lodestone attracting nails.png|thumb|Lodestone attracting some iron nails]]
[[Image:Magnetite Lodestone.jpg|thumb|Lodestone in the [[National Gem and Mineral Collection#Hall of Geology, Gems, and Minerals|Hall of Gems]] of the [[Smithsonian]]]]
[[Image:Lodestone (black).jpg|thumb|Lodestone attracting small bits of iron]]
'''Lodestones''' are naturally [[magnetization|magnetized]] pieces of the mineral [[magnetite]].<ref name="Dana">{{cite book 
  | last = Hurlbut 
  | first = Cornelius Searle 
  | author2 = W. Edwin Sharp 
  | author3 = Edward Salisbury Dana 
  | title = Dana's minerals and how to study them 
  | publisher = John Wiley and Sons 
  | year = 1998 
  | pages = [https://archive.org/details/danasmineralshow00hurl/page/96 96] 
  | url = https://archive.org/details/danasmineralshow00hurl/page/96 
  | isbn = 0-471-15677-9 
  | url-access = registration 
  }}</ref><ref name="Bowles">{{cite book   
  | last = Bowles
  | first = J. F. W. 
  |author2=R. A. Howie |author3=D. J. Vaughan |author4=J. Zussman
  | title = Rock-forming Minerals: Non-silicates: oxides, hydroxides and sulphides, Volume 5A, 2nd Ed.
  | publisher = Geological Society of London
  | year = 2011
  | location = UK
  | pages = 403
  | url = https://books.google.com/books?id=2GLGx6A0d0UC&q=lodestone&pg=PA403
  | isbn = 978-1862393158}}</ref>   They are naturally occurring [[magnet]]s, which can attract [[iron]].   The property of [[magnetism]] was first discovered in [[Ancient history|antiquity]] through lodestones.<ref name="Tremolet">{{cite book | last = Du Trémolet de Lacheisserie | first = Étienne |author2=Damien Gignoux |author3=Michel Schlenker  | title = Magnetism: Fundamentals | publisher = Springer | year = 2005 | pages = 3–6 | url = https://books.google.com/books?id=MgCExarQD08C&pg=PA3 | isbn = 0-387-22967-1}}</ref> Pieces of lodestone, suspended so they could turn, were the first [[magnetic compass]]es,<ref name="Tremolet" /><ref>{{cite web | last = Dill | first = J. Gregory | title = Lodestone and Needle: The rise of the magnetic compass | work = Ocean Navigator online | publisher = Navigator Publishing | date = Jan–Feb 2003 | url = http://www.oceannavigator.com/January-February-2003/Lodestone-and-needle-the-rise-of-the-magnetic-compass | access-date = 2011-10-01}}</ref><ref>{{cite book | last = Merrill | first = Ronald T. |author2=Michael W. McElhinny |author3=Phillip L. McFadden  | title = The Magnetic Field of the Earth | publisher = Academic Press | year = 1998 | pages = 3 | url = https://books.google.com/books?id=96APl4nK9lIC&q=lodestone+magnetic+compass&pg=PA1 | isbn = 0-12-491246-X}}</ref><ref>{{cite book | last = Needham | first = Joseph |author2=Colin A. Ronan  | title = The Shorter Science and Civilization in China | publisher = Cambridge Univ. Press | year = 1986 | location = UK | pages = 6, 18 | url = https://books.google.com/books?id=CjRAiqGSJ50C&pg=PA6 | isbn = 0-521-31560-3}}</ref> and their importance to early [[navigation]] is indicated by the name ''lodestone'', which in [[Middle English]] means "course stone" or "leading stone",<ref>{{cite encyclopedia | title = Lodestone | encyclopedia = Merriam-Webster online dictionary | publisher = Merriam-Webster, Inc. | year = 2009 | url = http://www.merriam-webster.com/dictionary/lodestone | access-date = 2009-06-12}}</ref> 
from the now-obsolete meaning of ''[[:wikt:lode|lode]]'' as "journey, way".<ref>{{OED|lodestone}}: 'Literally 'way-stone', from the use of the magnet in guiding mariners.'</ref>

Lodestone is one of only a very few minerals that is found naturally magnetized.<ref name="Dana" />  Magnetite is black or brownish-black, with a metallic [[lustre (mineralogy)|luster]], a [[Mohs scale of mineral hardness|Mohs hardness]] of 5.5–6.5 and a black [[streak (mineralogy)|streak]].

==Origin==
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]], or resistance to magnetization or demagnetization.<ref name="Livingston">{{cite book
 | last1  = Livingston
 | first1 = James D. 
 | title  = Driving Force: The Natural Magic of Magnets
 | publisher = Harvard University Press
 | date   = 1996
 | pages  = 14–20
 | url    = https://books.google.com/books?id=Xc_v9KUQaugC&q=Lodestone+magnetite+maghemite&pg=PA17
 | isbn   = 0674216458
 }}</ref>   Microscopic examination of lodestones has found them to be made of magnetite (Fe<sub>3</sub>O<sub>4</sub>) with [[inclusion (mineral)|inclusion]]s of [[maghemite]] (cubic Fe<sub>2</sub>O<sub>3</sub>), often with impurity metal [[ion]]s of [[titanium]], [[aluminium]], and [[manganese]].<ref name="Livingston" /><ref name="Wasilewski">{{cite journal
|doi=10.1029/1999GL900496
|first=Peter
|last=Wasilewski
|author2=Günther Kletetschka
 |title=Lodestone: Nature's only permanent magnet - What it is and how it gets charged
|journal=[[Geophysical Research Letters]]
|volume=26
|issue=15
|pages=2275–78
|year=1999
|bibcode = 1999GeoRL..26.2275W }}</ref><ref name="Warner">{{cite book
 | last1  = Warner
 | first1 = Terence E. 
 | title  = Synthesis, Properties and Mineralogy of Important Inorganic Materials
 | publisher = John Wiley and Sons
 | date   = 2012
 | pages  = 114–115 
 | url    = https://books.google.com/books?id=IR_IxoBT_S4C&q=Lodestone+magnetite+maghemite&pg=PA114
 | isbn   = 978-0470976029
 }}</ref>   This inhomogeneous crystalline structure gives this variety of magnetite sufficient [[coercivity]] to remain magnetized and thus be a [[permanent magnet]].<ref name="Livingston" /><ref name="Wasilewski" /><ref name="Warner" />

The other question is how lodestones get [[magnetize]]d.  The [[Earth's magnetic field]] at 0.5 [[gauss (unit)|gauss]] is too weak to magnetize a lodestone by itself.<ref name="Livingston" /><ref name="Wasilewski" />  The leading theory is that lodestones are magnetized by the strong magnetic fields surrounding [[lightning]] bolts.<ref name="Livingston" /><ref name="Wasilewski" /><ref name="Warner" /> This is supported by the observation that they are mostly found near the surface of the Earth, rather than buried at great depth.<ref name="Wasilewski" />

==History==
One of the earliest known references to lodestone's magnetic properties was made by 6th century BC Greek philosopher [[Thales of Miletus]],<ref>{{cite web | last = Brand | first = Mike | author2 = Sharon Neaves | author3 = Emily Smith | title = Lodestone | work = Museum of Electricity and Magnetism, Mag Lab U | publisher = US National High Magnetic Field Laboratory | year = 1995 | url = http://www.magnet.fsu.edu/education/tutorials/museum/lodestone.html | access-date = 2009-06-21 | archive-url = https://web.archive.org/web/20090501063207/http://www.magnet.fsu.edu/education/tutorials/museum/lodestone.html | archive-date = 2009-05-01 | url-status = dead }}</ref> whom the ancient Greeks credited with discovering lodestone's attraction to iron and other lodestones.<ref>{{cite book | last = Keithley | first = Joseph F. | title = The Story of Electrical and Magnetic Measurements: From 500 B.C. to the 1940s | publisher = John Wiley and Sons | year = 1999 | pages = 2 | url = https://books.google.com/books?id=uwgNAtqSHuQC | isbn = 0-7803-1193-0}}</ref> The name ''[[magnet]]'' may come from lodestones found in [[Magnesia ad Sipylum|Magnesia]], [[Anatolia]].<ref>The [[Ancient Greek|Greek]] term μαγνῆτις λίθος ''magnētis lithos'' (see [https://archive.org/details/bub_gb_BkS2KW7u76MC ''Platonis Opera''], Meyer and Zeller, 1839, p. 989) means "Magnesian stone". It is uncertain whether the adjective μαγνῆτις "of Magnesia" should be taken to refer to the city ''Magnesia ad Sipylum'' in [[Lydia]] (modern-day [[Manisa, Turkey]]) or after the Greek region of [[Magnesia (regional unit)|Magnesia]] itself (whence came the colonist who founded the Lydian city); see, for example, {{cite web|url=http://www.languagehat.com/archives/001914.php |title=Magnet |work=Language Hat blog |date=28 May 2005 |access-date = 22 March 2013}} See also: Paul Hewitt, ''Conceptual Physics''. 10th ed. (2006), p. 458.</ref> The [[History of India|ancient Indian]] medical text ''[[Sushruta Samhita]]'' describes using magnetic properties of the lodestone to remove arrows embedded in a person's body.{{citation needed|date=July 2024}}

<!-- The following is partly identical to [[Magnetism#History]] -->
The earliest Chinese literary reference to magnetism occurs in the 4th-century BC ''Book of the Devil Valley Master'' (''[[Guiguzi]]'').<ref>The section "Fanying 2" ([[:s:鬼谷子|反應第二]]) of ''The [[Guiguzi]]'': "{{lang|zh|其察言也，不失若磁石之取鍼，舌之取燔骨}}".</ref>
In the chronicle ''[[Lüshi Chunqiu]]'', from the 2nd century BC, it is explicitly stated that "the lodestone makes [[iron]] come or it attracts it."<ref>{{Cite book |title=Encyclopedia of Chinese History |last= Dillon |first= Michael |publisher= Routledge |year=2017 |isbn=978-0415426992 |pages=98}}</ref><ref name=Li54>{{cite journal |last=Li |first=Shu-hua |title=Origine de la Boussole II. Aimant et Boussole |journal=Isis |volume=45 |number=2 |year=1954 |pages=175–196|jstor=227361|doi=10.1086/348315|s2cid=143585290 | quote = un passage dans le ''[[Lüshi Chunqiu|Liu-che-tch'ouen-ts'ieou]]'' [...]: “La pierre d'aimant fait venir le fer ou elle l'attire.” | language = fr}}<br /> From the section "''Jingtong''" ({{lang|zh|精通}}) of the "Almanac of the Last Autumn Month" ({{lang|zh|季秋紀}}): "{{lang|zh|慈石召鐵，或引之也}}]"</ref> 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."<ref>In the section "[https://archive.org/stream/lunheng02wang#page/350/mode/1up A Last Word on Dragons]" ({{lang|zh|亂龍篇}} ''Luanlong'') of the ''[[Lunheng]]'': "[[Amber]] takes up straws, and a load-stone attracts needles" ({{lang|zh|頓牟掇芥，磁石引針}}).</ref> In the 2nd century BC, Chinese [[Geomancy|geomancers]] 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.<ref>{{Cite book |title=Echoes from Old China: Life, Legends, and Lore of the Middle Kingdom |last=Tom |first=K. S. |publisher=University of Hawaii Press |year=1989 |pages=108}}</ref><ref>{{Cite book |title=Chinese Fans: Artistry and Aesthetics  |last= Qian  |first= Gonglin |publisher=Long River Press |year=2000 |isbn= 978-1592650200 |pages=98}}</ref><ref>{{Cite book |title=The History of China: (The Greenwood Histories of the Modern Nations) |last=Curtis Wright  |first=David |publisher=Greenwood Publishing Group |year=2001 |pages=42}}</ref> While this has been shown to work, archaeologists have yet to discover an actual spoon made of magnetite in a Han tomb.<ref>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.</ref>

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.<ref name="Carlson1975">{{cite journal|last1=Carlson|first1=J. B.|title=Lodestone Compass: Chinese or Olmec Primacy?: Multidisciplinary analysis of an Olmec hematite artifact from San Lorenzo, Veracruz, Mexico|journal=Science|volume=189|issue=4205|year=1975|pages=753–760|issn=0036-8075|doi=10.1126/science.189.4205.753|pmid=17777565|bibcode=1975Sci...189..753C|s2cid=33186517}}</ref> Carlson speculates that the Olmecs, for astrological or [[geomancy|geomantic]] purposes, used similar artifacts as a directional device, or to orient their temples, the dwellings of the living, or the interments of the dead.<ref name="Carlson1975"/> Detailed analysis of the Olmec artifact revealed that the "bar" was composed of [[hematite]] with [[titanium]] lamellae of Fe<sub>2–x</sub>Ti<sub>x</sub>O<sub>3</sub> that accounted for the anomalous [[remanent magnetism]] of the artifact.<ref>[http://deepblue.lib.umich.edu/bitstream/handle/2027.42/23074/0000648.pdf?sequence=1 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]</ref>

"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..."<ref>Needham, ''Clerks and Craftsmen'', p. 240.</ref>

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 [[Margaret Cavendish, Duchess of Newcastle-upon-Tyne|Mary Cavendish]] in 1756, possibly to secure her husband's appointment as Chancellor of Oxford University.<ref>{{Cite web|url=https://mhs.web.ox.ac.uk/collections-online#/item/hsm-narrative-10530|title=Inv. 47759 - Sphaera article|last=Kell|first=Patricia|date=1996}}</ref> [[Isaac Newton]]'s signet ring reportedly contained a lodestone which was capable of lifting more than 200 times its own weight.<ref>{{Cite book|url=http://www.bitnick.it/Fonti/Thompson%20-%20Electromagnet.pdf|title=The Electromagnet, and Electromagnetic Mechanism|last=Thompson|first=Sylvanus|publisher=E. & F. N. Spon|year=1891|location=London|pages=128}}</ref> And in 17th century London, the [[Royal Society]] displayed a {{convert|6|in|cm|adj=on}} spherical lodestone (a ''terrella'' or 'little Earth'), which was used to illustrate the Earth's magnetic fields and the function of mariners' compasses.<ref>{{Cite web|url=https://pictures.royalsociety.org/image-rs-8487|title=A terella|website=The Royal Society Picture Library}}</ref> 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."<ref>{{Cite book|title=Sympathetic Attractions: Magnetic Practices, Beliefs, and Symbolism in Eighteenth-Century England|last=Fara|first=Patricia|publisher=Princeton University|year=1996|isbn=9780691634913|pages=23}}</ref>

== References ==
{{Reflist}}

== External links ==
{{wiktionary}}
* [http://www.phy6.org/earthmag/lodeston.htm Lodestone]

[[Category:Ancient Greek technology]]
[[Category:Electric and magnetic fields in matter]]
[[Category:Iron(II,III) minerals]]
[[Category:Oxide minerals]]