The material bronze was so essential to the development of human civilization that there is a whole epoch called “The Bronze Age” by historians and anthropologists. The academics put the Bronze Age as running from 4500 BCE to around 1400 BCE, followed by “The Iron Age.”
Bronze is not a naturally occurring metal – it is an alloy of copper and tin. The extraction of these two metals pre-dated the development of bronze, but in an act of historic neglect, no one talks about a “copper age.”
However, bronze was more easy to work into shapes than tin, and was stronger than copper. It was found to be a useful material from which to make swords, shields and spearheads. Anyone who has ever seen the larger than life size bronze statue of Poseidon at the National Archeological Museum in Athens, which was recovered from an ancient shipwreck in 1926, appreciates what can be wrought from this material.
Today, in the 21st century, bronze still has important applications – because it resists corrosion, many large ocean going vessels have propellers of cast bronze.
Bronze is mainly copper, with tin included for 9-14% of the alloy. No one today doubts the critical significance of copper to the modern world. Every year, mines produce about 20 million tons of new copper, and another up to 10 million tons comes from recycling. Copper wire and other forms of copper are re-melted to use again and again in new products. With higher copper prices – today nearing $10,000 a ton, up from $5500 a ton in 2017, and a pandemic generated low of $4500 a ton in 2020.
The trend toward mobile electrification, and non-carbon based energy supply make copper perhaps the key raw material for the next stage of technological development. In fact, one popular phrase is to call materials like copper and lithium “the new oil.” There is more poetry than accuracy in that phrase, since neither material generates energy – one stores, and the other transmits it.
What of tin, the other component of the bronze of the Bronze Age?
Tin is a far smaller, more modest metal market than copper. In 2021 there is about 300,000 tons of tin produced, world-wide. That was an 11% increase in production from the year before, reflecting a dramatic change in the tin price: having bounced around $20,000 a ton for the previous five years, in mid 2021 the price began to climb, to close to $44,000 in early 2022.
When the supply increases for a commodity by 11%, but the price more than doubles, this is a sure sign that the demand side of the market is growing rapidly.
In fact, tin is a high tech metal. Most people think of “tin cans” which is a mis-nomer anyway, since cans are made from steel, with what once was a thin coating of tin to prevent contact between oxidizable steel and things like food. Although this remains a major application for tin, as a material to be plated on steel, other materials are now used for that purpose as well.
Smartphones, computers or other electronic product them tiny bits of tin inside them, connecting power flows as solder. So small as to be invisible to users, this is an integral part of many advanced technologies which are part of everyday life today.
Tin’s high tech applications do not end there. In medical science magnetic resonance imaging machines (MRIs) there are superconducting magnets, which are made from a niobium-tin alloy, as there are in maglev trains. The particle accelerator at CERN, which has found elements that no one knew existed has a bank of superconducting magnets to drive protons down its “racetrack.” Tin is used in all of these applications.
Unlike copper, there are no “super-giant” tin mines. In fact, almost half the world’s tin is produced in an exceptionally low tech manner – by dredging the riverbeds of Indonesia and Malaysia. The largest producer of tin, however, is China, which produces tin from large, open cast mines. The largest of the Chinese producer is the Yunnan Tin Company, which produces about a quarter of the annual world production, and it is double the size of the second largest producer.
Interesting as tin is in the high tech area today, its potential for the future is even more dramatic, if scientists studying the production of hydrogen have anything to say.
The most common methods of hydrogen production currently are steam reforming of methane (natural gas) which generates lots of CO2 and requires a lot of energy, or electrolysis of water to separate the oxygen atoms from the hydrogen atoms in H2O, which does not produce any CO2, but requires lots of electric current. If a cheap, clean source of electricity is not available, the electrolysis method is as “dirty” as steam reforming.
A process known as “methane pyrolysis” is being developed, in which methane is heated in an oxygen-free environment, and passed through a medium that separates carbon atoms from hydrogen atoms, producing pure hydrogen and pure carbon, but no CO2 or other unwanted gases. One of the most promising elements for this process is molten tin in a fluidized bed.
Both copper and tin will be critically important to the future economy. Copper is well advertised as a strategic metal, and rightly so.
However, tin could become central to a hydrogen economy, with a role that the tin miners six thousand years ago could never have remotely imagined. But therein lies a warning: it is generally believed that the transition from the Bronze Age to the Iron Age, three thousand years ago was that new deposits of tin became harder to find, so that bronze production was increasingly restricted.
With the growing critical technology roles for both copper and tin, albeit as separate metals rather than alloyed, the future may come to be regarded as a new Bronze Age.