Materials through history

First Nations Australians' materials science

Aboriginal and Torres Strait Islander peoples have lived in Australia for at least 65 000 years. Over that time they developed sophisticated knowledge of the properties of local materials, passed on through generations, and matched each material carefully to its job.

• Stone tools: toolmakers chose stones such as quartzite, chert and silcrete that fracture to give sharp, predictable edges. Grinding a stone's edge against sandstone with water produced a tough, sharp axe. Some stone was heated in a fire before flaking, which changes its structure and makes it easier to shape into fine blades.
• Trade in stone: greenstone from the Mount William quarry in Wurundjeri Country (Victoria) made excellent axes because it is hard and tough. Axe heads from this quarry have been found hundreds of kilometres away, showing extensive trade networks.
• Adhesives: resin from spinifex grass and other plants was heated and worked into a strong glue to fix stone points onto spears and handles. It softens when warmed and sets hard when it cools, so tools could be repaired.
• Ochre: red, yellow and white earth pigments are coloured by iron oxides and other minerals. Ochre was mined, traded across the continent and used in ceremony, art and body paint, and to help preserve and protect skin and materials.
• Plant fibres and wood: spears were made from light, straight wood that was easy to throw; boomerangs and clubs from denser wood. Bark was stripped to make canoes (trees with "canoe scars" can still be seen), and baskets and bags woven from grasses, reeds and bark fibre could be tight enough to carry water or honey. Coolamons (carved wooden dishes) were used to carry food, water and even babies.
• Grindstones: grinding stones used to make flour from grass seeds are among the oldest evidence of seed grinding in the world.

The Stone, Bronze and Iron Ages

Archaeologists divide much of human history in Europe, Asia and Africa into ages named after the main material used for tools.

The Stone Age began over 3 million years ago, when early humans first chipped stones such as flint (a form of quartz) to make sharp edges. Wood, bone and shell were also used, but they rot, so few survive.

The Copper Age. Lumps of pure copper (native copper) can be found in a few places. Copper is soft enough to hammer into shape cold. But native copper is rare, and copper is too soft to keep a sharp edge. About 7000 years ago people discovered that heating green copper ores such as malachite with charcoal at very high temperatures released the metal. Extracting a metal from its ore using heat is called smelting. The charcoal does two jobs: it burns hot, and the carbon in it pulls oxygen away from the metal.

The Bronze Age. Metalworkers found that adding about 10% tin to copper produced bronze, an alloy much harder than either metal. Bronze tools and weapons held a sharp edge, and broken ones could be melted down and recast. Copper and tin ores are rarely found in the same place, so long-distance trade grew: tin from Cornwall in England reached the Middle East. Many historians think the need to keep track of trade helped writing spread.

The Iron Age. Iron ore is far more common than tin, so iron could be cheaper. But iron is harder to smelt: early furnaces couldn't melt it, producing instead a spongy lump that had to be hammered while red hot (forging; hence "strike while the iron is hot"). Smiths later learned that iron heated with charcoal absorbs a little carbon and becomes steel, which is much harder and tougher than bronze. Iron ploughs and steel tools transformed farming and warfare.