Evolution of Metallurgy

Definition of Metallurgy

  • Three definitions to consider:

    • Art and science of extracting metals from ores and modifying them for use (emphasizes smelting).
    • Process used for the extraction of metals in their pure form (similar to the first definition).
    • System of manufacturing, distributing, and using metals and metal objects (focuses on metal usage, proposed by archaeologists White and Hamilton).

  • Traditional view: Metallurgy began with smelting (6,000-5,000 years ago).

  • Alternative view (White and Hamilton): Considers all metal usage over the past 10,000 years, encompassing a pre-metallurgy period.

Archaeometallurgy

  • Interdisciplinary field examining all aspects of metal production, use, and consumption over the past 10,000 years.

  • Subdivision of archaeology.

  • Two main groups:

    • Archaeologists studying ancient metals.
    • Metallurgical engineers studying archaeology.

  • Engineering side: Focuses on material science and scientific analysis.

  • Archaeology side: Focuses on human interaction with metals and their impact on human societies.

Global Use of Metals

  • Chart by Muhly (2012) summarizes global metal use.

  • First metal used: Native copper (10,000 years ago).

  • Later: Gold, silver, bronze, arsenical bronze, tin bronze, brass, iron.

  • Very recent: Aluminum (late 19th century CE).

  • Chart also shows metal abundance in Earth's crust (e.g., iron and aluminum are abundant; gold is rare).

Early Metallurgy

  • Focus on metal use, not just smelting.

  • Metals used in raw, native form (e.g., gold, native copper).

    • Gold is almost exclusively found in native form.

  • Native metals are pure enough to use directly.

Metallurgical Revolution

  • Development of smelting didn't immediately lead to total metal use.

  • Early metal use was a slow process.

  • Metals coexisted with older technologies (stone, bone tools).

  • Metal tools often replicated earlier tool forms.

  • Metal adoption was gradual; not all societies adopted metal as a dominant technology.

  • Early metal use was often driven by symbolic value (luster, color, ductility, malleability) rather than just utilitarian function.

  • It's important to consider the cultural context of metal use, not just assume tools were solely for practical purposes.

Copper

  • Earliest evidence of copper usage: Native copper, 10,000 years ago.

  • Copper was hammered and annealed (heated to 200-225 degrees Celsius to regrow crystals).

  • Earliest site: Caenum Tesepe in Anatolia (Turkey).

  • Copper used for small ornamentations; metallurgy didn't take off for another 5,000 years in the Old World.

Native Copper Industry in North America (Great Lakes)

  • Dates back to about 9,500 years ago.

  • Potentially one of the oldest metallurgical industries; first organized use of metals globally.

  • People accessed large deposits of native copper (largest in the world) in bedrock sites.

    • Michigan's Upper Peninsula, Keweenaw Peninsula, Isle Royale.

  • Archaeologists use sediment cores to track pollution levels (lead) from copper mining to date activity.

  • Informal mining: Part-time activity, often seasonal (e.g., summer on Isle Royale).

  • People moved seasonally and combined mining with other activities (fishing, collecting maple sap).

Sources of Copper

  • Glacial float copper: Glaciers picked up copper and deposited it across the Midwest.

Wisconsin has very large deposits.

  • Direct mining of copper veins exposed after glacial recession.

Copper Mining Process (Martin's Four Steps)

  1. Finding the copper to mine.

    • Looking for copper veins or known locations.

  2. Removing overburden.

    • Removing rocks, topsoil, trees, etc., from the deposit.

  3. Initial hammering.

    • Crushing the matrix away from the copper.
    • Fissure mines: Following cracks in the ground.
    • Load mines: Hammering around large chunks of copper.

  4. Precision hammering.

    • Targeting the material around the copper, removing poor rock and waste rock.

  5. Breaking down and forming the copper.

    • Hammering off matrix pieces and shaping the copper for transport.

Fire Setting

  • Debate on whether fire setting (heating rock with fire, then dousing with cold water) was used to aid mining.

  • Proposed due to charcoal found at sites.

  • Tyler Bastian's experiment in the 1960s: Unsure if it was efficient.

  • Katie Trotter's research: Suggests it was a viable method.

Mining Locations

  • Historic map by Charles Whittlesley shows ancient mining pits on the Keweenaw Peninsula.

  • Mining sites resemble the surface of a golf ball (pitted).

  • Pits range from half a meter to several meters deep.

Copper Working

  • Cold hammering and annealing (heating and reshaping) was used.

  • No smelting or melting technologies developed in the Great Lakes.

  • Anvil stones and rounded hammerstones were used.

  • Annealing involved heating copper in a fire and cooling it.

  • Typical piece required 10-50 annealing cycles.

  • Debate on whether hot or cold working was used.

  • Grinding used as a final finishing tool.

  • Other techniques: Cutting, riveting, slotting, molding, polishing.

Copper Production Sequence (Example: Awl)

  1. Piece of rock copper

  2. Initial hammering

  3. Forming into a bar

  4. Preform (initial shaping)

  5. Finished awl (perforating tool)

Technological Shifts in Native Copper Industry

  1. Old Copper Complex (Archaic Period, 9,500-2,500 years ago)

    • Centered in Eastern Wisconsin; used float copper.

    • Large, heavy, bulky, utilitarian tools (spear points, knives, awls, fish hooks).

    • Also bracelets, pendants, rings, and beads.

  2. Shield Archaic (Contemporary with Old Copper Complex)

    • Located north of Lake Superior in the Canadian Shield.

    • Hunting and gathering complex; similar utilitarian tools with emphasis on woodworking and fishing.

  3. Hopewell Culture (Woodland Period, 100 BC - 400 AD)

    • Centered around mound sites in Ohio and Illinois.

    • Increase in complexity, elaborate mortuary ceremonialism, mound construction.

    • Consumption of prestige and exchange goods (Hopewell Interaction Sphere).

    • Copper from the Great Lakes used for ornate, symbolic, and ritualistic items (bracelets, breastplates, geometric sheets, beads).

    • Utility tools still used; continuation of bead and bracelet making.

  4. Mississippian Period (900 AD to European Contact)

    • Centered around the Mississippi River Basin.

    • Exemplified by maze-based farming, settled villages, and complex social systems.

    • Standardization of art styles and long-distance trade of exotic goods.

    • Copper used for hair ornaments, gorgets, beads, headdresses, ear spools.

    • Continued use of utilitarian items.

    • Copper primarily used for prestige goods at ceremonial centers like Cahokia and Angel Mounds.

    • Standard templates used for crafting copper items.

Copper and Indigenous Beliefs (Ojibwe)

  • Copper Manitou: Supernatural beings associated with copper.

    • Examples:
      • Mishibisi (Underwater Panther): Chief of water spirits and guardian of copper.
      • Mishigunabeg (Great Serpent): Largest and strongest underwater Manitou; scales and horns made of copper; responsible for drownings and harm; sacrifices yield good hunting, fishing, safe passage, and medicinal powers.

Copper Smelting (Old World)

  • Began around 6,000 years ago.

  • People melted and cast native copper.

  • Smelting: Heating ore to melting point and reducing metal into a metallurgical material.

  • Uses oxidizing agents (air) or reducing agents (coke, charcoal).

  • Goal: Separate impurities from ores.

  • First fuel used: Charcoal (produced by baking wood with limited oxidization).

  • Earliest evidence: 5000 BCE in Serbia and Iran.

  • Later: Independent development in South America.

Alloys (Combination of Two or More Metallic Elements)

*   First Alloy: Bronze

*   Arsenical Bronze: Alloyed with arsenic.