FIRST YEAR ARCHAEOLOGY

TUTORIAL 15

EARLY IRON METALLURGY

THE IRON AGE IN IRELAND

Definition of term ‘IRON AGE’

TECHNOLOGICAL MEANING

Iron-using societies

THE IRON AGE IN IRELAND

Definition of term ‘IRON AGE’

TECHNOLOGICAL MEANING

First contact with iron 700 – 500 BC

Adoption of iron technology 300 BC onwards

Influence of Roman technology from 1st century AD

Expanded use of iron in early medieval period (500 – 1200 AD)

Technological influence of Viking World after 900 AD

THE IRON AGE

EARLY IRON WEAPONS

IRON SWORDS

Drumlane iron cauldron

Co. Cavan

Drumlane iron cauldron

Co. Cavan

Influence of Late Bronze Age

metalworking traditions on the

first ironworking in Ireland

Lough Mourne iron axehead,Co. Antrim

Can see this also in case of earliest iron axeheads > copies of bronze axeheads

Sources of Iron in Early Ireland

Pure iron: very rare.

Use of meteoric iron by some early cultures, but not in Ireland.

Early Ireland: probable use of 2 sources: bedrock ores & bog ores.

Examples: Haematite (Fe2O3) and Limonite Fe2O3H2O).

No early iron mines discovered in Ireland.

Probably surface extraction of bog ores, leaving little archaeology.

Ore Preparation

Cleaning (washing) and concentration (hand-picking) of ores

Roasting of ores to expel water

SMELTING OF IRON ORES

Early iron workers were not able to melt iron to be able tocast it into moulds > required the development of the blast furnace in later medieval times.

In earlier times, iron was produced by the Bloomery Process,in the same 1200˚C temparature range as bronze casting.

This involved the solid state conversion of iron ore to iron metal, without the iron ever entering the liquid stage.

This produced Blooms of impure ironThis happens through the production of carbon monoxide gas in The furnace, which reduces the iron ore:

Fe2O3 + 3CO 2Fe + 3CO2

IRON SMELTING

REQUIRED THE

USE OF A

FURNACE

Excavation

evidence of a

early furnace

Slag Pit

Furnace

Tuyere

IRON SMELTING

SMELTINGSLAG

Converting the bloom of ironinto pure iron

Heating it and hammering it hotto squeeze out impurities

THE IRON SMITHFORGING IRON OBJECTS

CASTING BRONZE OBJECTS

IS DIFFERENT !

Involves pouring

molten metal into

Crucibles and Moulds

IRON

SMITHING

TOOLS

Iron is a pure metal; Steel is an alloy of Iron (that has absorbed carbon)

All iron produced in prehistory was impure > Wrought Iron

This impure iron can be converted to Steel by a process called Carburization

HOW EARLY IRON AXEHEADS WERE MADE IN IRELAND

Forging theFeerwore axeheadfrom Co. Galway

Lough Mourne iron axehead,Co. Antrim

VIKING IRON OBJECTS

PRESERVATION OF

IRON OBJECTS

IN ARCHAEOLOGICAL

CONTEXTS