Metals of one sort or another make up about a quarter of the Earth's crust, although except for gold and the platinum metals almost always in the form of compounds with other substances. The rocks or minerals from which metals can be extracted are called ores. Metals can be arranged in a list in an order of reactivity. Here are a few selected metals in their order of reactivity, the most reactive first.
The first metal to be produced in a reasonably pure form was gold. Gold is so low in the order of reactivity that it does not often form compounds with other elements. This means that it usually exists in the Earth's crust native, as grains or even nuggets of almost pure gold, and not in the form of compounds, so it only needs to be separated from the surrounding rock by very simple processes. No chemical processes are involved, although the process is very hard work and takes a long time. You may have seen Western films showing gold prospectors panning for gold; today you can pan for gold at Theme Parks.
Copper came after gold. Extracting copper involves a chemical process, but only technology based upon a simple wood fire. Tin and lead came next - these need more advanced technology and higher temperatures.
Then came iron - this needs very high temperatures, far higher than can be produced in an ordinary wood fire. These temperatures can only be produced inside a blast furnace, where air is forced at high pressure into the middle of burning charcoal or coke.
Metals above iron in the order of reactivity are very hard to separate from their compounds and few were isolated until the eighteenth century CE.
There is a list of many common and not so common metals on another page of this web site - to link to it click here 
A mixture of a metal with another metal or another substance is called an alloy. Alloys usually have physical properties such as hardness or melting point quite unlike the metals in them. Many alloys are harder than and have a lower melting point than the metals in them, and in the past it was these properties which made them useful. Many alloys have been known and used for hundreds or thousands of years, and some of these are discussed next. Recently however whole ranges of alloys with totally new properties have been developed. You can read about these at the end of this Page.
Pure gold is very soft indeed and useless for anything except objects such as ornaments and jewellery. In Europe and North America it is almost always alloyed with another metal (usually copper) to make it harder.
The purity of gold is measured in carats. Pure gold is twenty four carat. Twenty two carat gold is twenty two parts of gold and two parts of copper (adding up to twenty four), eighteen carat gold is eighteen parts of gold and six parts of copper, and so on.
An alloy of gold and silver is sometimes called electrum. Electrum is much harder than pure gold. In Ancient Egypt there were lots of gold mines but no silver mines. Silver was imported from the Northern Mediterranean, but was very little used. But they did use electrum instead of pure gold for objects to be left out of doors, for example pyramidions (the very tip of pyramids and obelisks), because pure gold would wear away too quickly during sandstorms.
The carat used for describing the purity of gold is not the same as the carat used for weighing precious stones such as diamonds. The carat used for weighing diamonds comes from the Arabic word qirat, meaning little weight. This carat was originally the mass of one of the seeds of the carob plant, and is about 200 mg.
Gold is always weighed in Troy ounces. A Troy ounce is about 31 g whereas an ordinary ounce is about 28 g, so an ounce of gold really does weigh more than an ounce of feathers!
Gold is very soft and can easily be made into jewellery and other beautiful things. It has been used in coinage for thousands of years, and it is also used as bullion (blocks of gold just stored in bank vaults for their value).
In electronic equipment such as computers and digital cameras copper connectors tarnish quite quickly and this affects their ability to conduct electricity. So the connectors are often gold plated as gold never tarnishes.
In Britain it is illegal to call something gold unless it is hall-marked. So most gold jewellery made in countries such as India cannot legally be sold in Britain as gold even though it may actually be twenty two carat gold.
Copper was the first metal to be extracted from the Earth that was hard enough to be used for purposes other than jewellery. It was used for axes, knives, ox shoes, hoes and other early agricultural tools, and also for weapons of hunting and warfare.
The earliest copper object so far found dates from about 9000 BCE. But it was another five thousand years before Man learnt to alloy copper with tin to make bronze - bronze is much harder than copper. Typically bronze is about 90% copper and 10% tin. However most of the stories from Greek mythology are set in the Bronze Age, and until recently most archaeologists referred to the whole of the period in which copper was used as the bronze age. The problem has been made worse by the fact that the Greeks used the same word khalkos for both copper and bronze. Now that we have a much better understanding of other early civilizations, archaeologists prefer the term chalcolithic (copper/stone) age for the period prior to the introduction of bronze. Although the Ancient Egyptians made some use of bronze, they also continued to use untinned copper, even for weapons, right up to the coming of iron, and used separate words for copper and bronze.
Bronze has a lower melting point than copper and can be cast very easily, that is, you can pour the molten metal into a mould to make objects of different shapes.
Some of the tin needed to make bronze came from Cornwall. There was trade between Cornwall and the Mediterranean at the time the Pyramids of Egypt were being built - two thousand years before the Romans came to Britain!
Pewter and brass have been widely used since Roman times. Pewter is an alloy of tin with varying amounts of lead, copper and other substances, and brass is an alloy of copper and zinc. (Although zinc was not separated as a metal until the thirteenth century CE brass was being made in India from ores naturally containing both copper and zinc before 1000 BCE, although it was not widely used in Europe and the Near East until Roman times.)
It is quite safe to drink out of pewter tankards and goblets, but you should not store liquids in them. This is because lead is slightly soluble in water, and significantly more soluble in acidic solutions, and drinks which have been stored in pewter vessels may have dangerously high concentrations of lead.
Solders are low melting point alloys used for joining or repairing metals and metal objects. Soft solder is an alloy of tin and lead, and is widely used for joining wires in electrical equipment and for many other purposes. Hard solder is an alloy of copper and zinc and is used in brazing (joining and repairing brass) - the proportions of the copper and zinc in hard solder are different from those in brass and so it has a much lower melting point than brass.
Iron is extracted from its ores by heating the
ore with carbon (initially charcoal but later coke) and limestone in
a blast furnace - the limestone combines with many of the
impurities, particularly silicates, in the ore to make a slag. The earliest blast
furnaces operated at a temperature high enough to melt the slag
(which is essential), but not high enough to melt the iron.
This meant that you could only make iron in batches, and
after you had made a batch of iron you had to
let the blast furnace cool and dismantle it to get the
lump of iron out. This lump of iron was called a bloom.
The iron produced in this way contained
almost no carbon and was pure enough to be immediately suitable
for making into tools and other objects by heating the lump of iron to
red-hot to soften it (make it malleable) and hammering it into
shape, as today a blacksmith makes horseshoes in his forge -
iron becomes malleable at a temperature a lot lower than that
needed to melt it. The iron produced in this way is called wrought iron. Wrought iron is not very hard, and tools made from wrought iron lose their edge very quickly, although of course they can easily be made sharp again. Also bronze can be cast whereas wrought iron cannot be, so bronze continued to be used for very many purposes a long time after the introduction of iron.
Later blast furnaces operated at a temperature high enough to melt the iron. The molten iron collects at the bottom of the blast furnace and can be run off at intervals without having to stop the furnace. However it also allows the molten iron to mix with the carbon, and as a result the material produced in such a blast furnace is actually an iron alloy containing about 4% carbon. This can be cast in a mould to make different objects so it is called cast iron. Cast iron is much harder than wrought iron, but it is also very brittle and cannot be reshaped once it has been cast. Hammering an object made of cast iron, even if it is heated until it is red hot, will shatter it.
Much more useful than either wrought iron (0% carbon) or cast iron (4% carbon) are alloys containing about 1% to 2% of carbon. Changing the amount of carbon in the iron, whether by adding carbon to wrought iron or removing carbon from cast iron, is called steelmaking, and the alloys produced in this way are called steels. You can read about the development of steelmaking by visiting the History of Steel website - to do so click hereSteel-making did not become economically feasible on a large scale until the introduction of the Bessemer process in the 1850s (CE). In this process oxygen is blown through molten cast iron using special hollow tubes. This oxidizes the carbon and the process is continued until the carbon content has been reduced to the right amount.
Today other substances such as chromium or nickel are sometimes added to the iron during the steelmaking process. Different steels have different properties which make them suitable for different purposes, but all steels contain at least 70% iron, and we often use the words iron and steel indiscriminately, as the Greeks used khalkos for both copper and bronze (see above).
Until Man learned how to extract iron from its ores by smelting all iron came from meteorites and was more valuable than gold. For more about meteorites please see the page on shooting stars. There was a dagger made from meteoric iron in Tutankhamen's tomb (about 1330 BCE). Meteoric iron contains no carbon so can be wrought; it also contains a small amount of nickel so does not rust!
Man first discovered how to extract iron by smelting about 2000 BCE in Asia, but the technology spread very slowly and did not reach the Mediterranean countries until about 1000 BCE. Countries which knew how to make iron were very careful to try to keep the technology to themselves, as today countries with nuclear weapons try to keep others from having them. The story of David and Goliath is set at the time of the transition from the Bronze Age to the Iron Age and you can find out more about it by clicking here
The carbon used in a blast furnace must be very pure: wood cannot be used because it contains sulphur, phosphorus and other substances which would get into and spoil the iron. So only charcoal could be used, and this made iron very expensive. The Industrial Revolution began when a method of making iron using coke (made from coal) rather than charcoal (made from wood) was discovered, which brought down the cost of iron.
Mercury is a liquid at normal temperatures, and forms an alloy on contact with any other metal. This is called amalgamating, and an alloy containing mercury is called an amalgam. Amalgams have very different properties from the original metal, and for all practical purposes mercury destroys any metal with which it comes into contact. It is particularly destructive of gold, and very great care should be taken to avoid even the least contact between mercury and gold jewellery. A married woman should always remove or cover up her gold wedding ring before cleaning up the pieces of a broken mercury thermometer - make certain your Mum knows this!
Platinum is a noble metal like gold and occurs native in the Earth's crust. It is however very much harder than gold and has a very much higher melting point. It is therefore very difficult to purify and make things out of, and although it was known in ancient times very little use was made of it until the end of the nineteenth century. It has almost never been used as bullion or in coinage.
Platinum jewellery was quite fashionable, among both men and women, at the beginning of the twentieth century, but is much less fashionable, particularly among women, today. Women tend not to like it because they think their beautiful platinum brooch might be mistaken for silver, a much cheaper metal.
Because of its chemical inertness, hardness, and other properties, platinum and platinum alloys are widely used in industry. The catalytic converter in the exhaust systems of most modern cars contains platinum.
Platinum is usually found with and is very similar to palladium, rhodium, iridium, osmium and ruthenium, and these are therefore referred to as the platinum metals. Osmium has the highest density of any metal, and an alloy of platinum and ruthenium is, after diamond, one of the hardest materials known to Man, and is used in the finest surgical instruments.
