Editing Tin (section)

==History==
{{Main|Tin sources and trade during antiquity}}
[[File:Sword bronze age (2nd version).jpg|thumb|Ceremonial giant bronze [[dirk]] of the Plougrescant-Ommerschans type, Plougrescant, France, 1500–1300 BC]]
Tin extraction and use can be dated to the beginnings of the Bronze Age around 3000&nbsp;BC, when it was observed that [[copper]] objects formed of [[polymetallic]] [[ores]] with different metal contents had different physical properties.<ref>{{Cite book|last1=Cierny|given1=J.|surname2=Weisgerber|given2=G.|date=2003|chapter=The "Bronze Age tin mines in Central Asia|editor1-last= Giumlia-Mair |editor1-first= A.| editor2-last= Lo Schiavo| editor2-first= F.|title=The Problem of Early Tin|pages= 23–31| location= Oxford| publisher= Archaeopress|isbn=978-1-84171-564-3}}</ref> The earliest bronze objects had a tin or arsenic content of less than 2% and are believed to be the result of unintentional [[alloying]] due to trace metal content in the copper ore.<ref name = "pen1986">{{Cite book| last= Penhallurick |first= R. D.|date= 1986| title= Tin in Antiquity: its Mining and Trade Throughout the Ancient World with Particular Reference to Cornwall|location=London|publisher=The Institute of Metals|isbn=978-0-904357-81-3}}</ref> The addition of a second metal to copper increases its hardness, lowers the melting temperature, and improves the [[casting]] process by producing a more fluid melt that cools to a denser, less spongy metal.<ref name = "pen1986" /> This was an important innovation that allowed for the much more complex shapes cast in closed [[Molding (process)|molds]] of the Bronze Age. [[Arsenical bronze]] objects appear first in the Near East where arsenic is commonly found with copper ore, but the [[Arsenic poisoning|health risks]] were quickly realized and the quest for sources of the much less hazardous tin ores began early in the Bronze Age.<ref>{{Cite book|editor1-last=Lamberg-Karlovsky|editor1-first=C. C.|editor2-last=Franklin|editor2-first=Alan D.|editor3-last=Olin|editor3-first=Jacqueline S.|editor4-last=Wertime|editor4-first=Theodore A.|editor4-link=Theodore Wertime|date=July 1980|journal=Technology and Culture|volume=21|issue=3|pages=474|doi=10.2307/3103162|chapter=The development of the usage of tin and tin-bronze: some problems |title=The Search for Ancient Tin|location=Washington D.C.|publisher=A seminar organized by Theodore A. Wertime and held at the Smithsonian Institution and the National Bureau of Standards, Washington D.C. March 14–15, 1977|jstor=3103162}}</ref> This created the demand for rare tin metal and formed a trade network that linked the distant sources of tin to the markets of Bronze Age cultures.<ref>{{cite web |title=Project Ancient Tin |url=https://projectancienttin.wordpress.com/}}</ref>

[[Cassiterite]] ({{chem|SnO|2}}), the oxide form of tin, was most likely the original source of tin. Other tin ores are less common [[sulfide]]s such as [[stannite]] that require a more involved [[smelting]] process. Cassiterite often accumulates in [[alluvial]] channels as [[placer deposits]] because it is harder, heavier, and more chemically resistant than the accompanying [[granite]].<ref name = "pen1986" /> Cassiterite is usually black or dark in color, and these deposits can be easily seen in [[river banks]]. Alluvial ([[placer deposits|placer]]) deposits may incidentally have been collected and separated by methods similar to [[gold panning]].<ref>{{cite journal |last1=Dube |first1=RK |title=Interrelation between gold and tin: A historical perspective |journal=Gold Bulletin |date=September 2006 |volume=39 |issue=3 |pages=103–113 |doi=10.1007/BF03215537 |doi-access=free }}</ref>