Iron

Ironworking spreads from Anatolia around 1200 BCE, after centuries of rare iron objects. Iron ore is common. The problem was heat and skill. A bloomery furnace does not melt iron the way bronze is melted. It makes a spongy mass that has to be hammered.

The contribution is strong metal in quantity. Nails, plowshares, swords, and later rails, bridges, and engine blocks are iron or its alloy, steel. A steam engine is an iron machine. A robot arm is steel, motors, and a chip. Remove iron and those machines have no body.

Steel is iron with a controlled amount of carbon. Good steel is later and harder to make. Much of the ancient 'iron age' is wrought iron, not modern steel. The industrial breakthrough in cheap steel is the nineteenth century, two and a half thousand years after this card.

The 1200 BCE date is the spread, not the first smelted piece. Iron shows up earlier as a prestige metal.