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GeneralNatural Sn-Cu Alloys

17th Aug 2019 15:32 UTCRichard Dale Expert

I am looking at ancient history of tin mining and there are two artifacts that seem too early for intentional metallurgy... therefore, could they be native alloys? One is a tiny awl from Tel Tsaf in the southern Levant, made c. 5000 BC, copper w/ about 6% tin. The other a hammered bead from Aurchlo l in Georgia, copper w/ 8.4% tin, c. 5600 BC. Both are heavily corroded, so original analysis would have been different.  Mining & metallurgical technology at Mushiston came MUCH later; occurrence of UM1965-07-E:CuSn, Sorosite, and ETA bronze seem to be sub-mm. blebs.  Any thoughts about bigger pieces of native bronze anywhere?

17th Aug 2019 17:29 UTCAlfredo Petrov Manager

Although the deliberate creation of bronze only started around 3,500 BC, simple smelting of copper ores started around 5,000 BC. So if someone had some copper ore with a bit of cassiterite or stannite in it, maybe they unintentionally got a few percent Sn in their copper? 

18th Aug 2019 10:17 UTCLuís Martins 🌟

I agree, bronze was probably first made by chance, by using impure ores.

19th Aug 2019 14:33 UTCRichard Dale Expert

Thanks, guys. If I recall correctly, simply mixing cassiterite with copper "oxide" ores maxes out at about 1% tin in the product.  To get more, it has to be intentionally layered with charcoal, so stannite, etc. had to be the culprit... I guess transported from one of those 'Stan areas.

19th Aug 2019 14:45 UTCJolyon Ralph Founder

What about when mixing in 'recycled' copper items into a mix with impure copper ores? Throwing unwanted broken tools into the furnace to be re-melted with fresh ore might change things.

 
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