The magic of metals

From a minerals perspective, Earth is the lucky planet. 

More than 98 percent of matter in the universe is made of hydrogen and helium, the two lightest gases, the stuff of which stars are made. So, bits of rock like our Earth are rare indeed. We stand on minerals, and our lives have ever depended on them.

Ages of metals

Starting with Stone, the Ages of humankind progressed through Copper (from 6000BC), and into Bronze, a highly-sought after alloy of copper and tin (from 3000BC). The Iron Age arrived around 1200BC with furnaces hot enough to smelt iron oxides, noting this metal, and nickel, was long known from meteorites. Adding a little carbon to iron made steel. Silver and gold were used for adornment. Lead and tin, together, made pewter.

Metal-bearing compounds were widely used in antiquity. Calcium carbonate (limestone) when heated to form lime (calcium oxide), crushed and mixed with water, was the Romans’ cement. Cobalt compounds had long-standing use in the colouring of glass/ceramics and in paints. An iron oxide, magnetite, powered the navigational compass. Sodium chloride has long been used as table salt.

So began the discovery and use of new materials and metals, with some hard lessons also learned along the way. Powdered antimony, a heavy metalloid, was the black eye liner used in Ancient Egypt. Mercury was used in ancient Chinese medicines to prolong life – the liquid metal probably had the opposite effect. Well-to-do Romans used lead in their plumbing.

The rise of chemistry

The art of separating elements and compounds out of the earth and rock from which they came has long captivated humanity. “Alchemy” was the application of myth, magic, religion - and trial and error - to transmute base metals into gold, create the “philosopher’s stone”, cures for all ills, and the “elixir of life”. Needless to say, none of these things were found but many others were instead. The alchemists developed many methods still used today – to extract metals from ores, distil volatile chemicals, control chemical reactions, metalworking - as well as inks, dyes, paints, gunpowder, leather tanning and many other practical applications.

In the 1600s Robert Boyle coined the term “chemistry”. The discovery of, and manufacture of materials took a scientific bent, as part of the revolution of ideas and experimentation that started with Galileo Galilei and, later, Isaac Newton.            

Over the next century in Europe many discoveries of metals were made. As a sample, cobalt was isolated in 1735, followed by nickel (1750s), manganese (1770), chromium (1780), molybdenum (1781), tungsten (1783), titanium (1795), magnesium (1808), lithium (1817), and aluminium (1825).

New frontiers

By 1863 there were 56 known elements – in contrast to the ten known in antiquity - with a new one being discovered every year. Dmitri Mendeleev was one of several chemists who noticed that the elements could be ordered in a sequence from lighter to heavier, based on atomic weight. He also noticed a cycling in the chemical properties of the elements. For example, calcium (element number 20) is similar to strontium (38) and barium (56) in its behaviour, and unlike the elements close to it in weight.

Mendeleev’s particular genius was to construct a table of elements, with several rows, each going from lighter to heavier, in such a way that groups like the “alkaline earth metals” – calcium, strontium and barium – appear above each other in columns. Similarly, the “noble metals”, copper (29), silver (47) and gold (79), form another column. There were a lot of gaps in the table in 1871, from which Mendeleev deduced the existence of eight elements then unknown to science, among them, gallium and germanium. These two metals were discovered in 1887 and 1886.

Paris-based Marie and Pierre Curie were, perhaps, the most well-known chemists of this era, with their pioneering work on radioactivity. In 1898 the Curies discovered two radioactive elements, polonium and radium. This work eventually cost Marie her life, after persistent exposure to radioactivity. She was recognised with two Nobel Prizes, in physics (1903) and chemistry (1911), the only person to be so recognised.               

The late 1800s and the 20th Century saw the completion of discoveries of the 15 lanthanide metals (rare earth elements), and the heavier actinides. The latter are radioactive, e.g., uranium (92), and most of them – e.g., plutonium (94) - are created synthetically in the laboratory. The heavier they get, the more unstable they become, with the half-life of lawrencium (103) being a few hours. That means that of a kilogram of this metal, only 5 grams would still exist after 36 hours. The rest would have decayed radioactively into lighter metals.

The pursuit to complete the last row of the Periodic Table borders on the surreal - it is questionable whether elements 104–118 exist in any meaningful sense. These things are produced as individual atoms in high-energy collisions, and almost instantaneously decay into something else. The heaviest known element, livermorium (116), was officially recognised by the International Union of Pure and Applied Chemistry in 2011.

Learn more about the periodic table of elements on http://www.chemicool.com/    

Metals today

Metals are used today in almost every facet of life, in construction, home and work, industry including primary production, energy generation and transmission, information technology, electronics, water supply, medicine, communications, transport, logistics, defence and warfare, and more besides.

To understand just how important the discoveries of metals have been to humankind, consider:

  • The metals used in x-ray tubes are one of, or a combination of: tungsten, molybdenum, copper, rhenium, cobalt
  • Electronics makes use of semi-conductors, such as gallium and germanium
  • Electric motors, computer hard drives, transformers, generators and electromagnets require ferromagnetic metals, chiefly: iron, nickel, cobalt, and some rare earth elements
  • Internal combustion engines and jet engines rely on alloys of steel with metals such as titanium, vanadium and tungsten
  • Batteries in common use as a source of electricity are made of metals such as: zinc, nickel, lithium, cadmium, lead and silver
  • Electricity generating nuclear fission reactors use uranium and/or plutonium

Other examples of how metals and other minerals are used are provided at http://www.straterra.co.nz/mining4nz/why-mine-in-nz/everyone-uses-minerals/ and http://www.straterra.co.nz/mining4nz/endangered-metals/