Main index --- Minerals list

Properties of natural materials

Cave painting Red Hematite This site only deals with natural, inorganic materials, either minerals that can be found in the ground (if you know where to look!), or the metals that can be extracted from these minerals. It does not cover manmade materials, such as plastics. It also does not cover materials such as leather or wood, that originally come from living animals or plants.

Mankind has known how useful minerals and rocks have been for a very long time indeed. In fact, all the earliest tools that we know about are all minerals, since organic materials have rotted away, and manmade materials are very recent. The earliest tools discovered are of stone, of flint or obsidian. The earliest pictures are cave paintings made with hematite (see right). Gradually mankind learned to make tools with metal, first with copper and bronze, then iron and steel. Steel is mainly iron, but has other metals in as well.

flint arrow Copper crystal So why use these particular materials? All these tools have a sharp edge. When we talk about the "Stone Age" or the "Bronze Age" or the "Iron Age", we don't mean that ALL tools were made of stone, bronze or iron. Wood has always been used, and stone and bronze are still used today. The tools that named the age were the tools with an edge. Flint and obsidian have the important property that when you hit them, they splinter into sharp flakes. You didn't need to sharpen them since they were already sharp. All you had to do was shape them. So why aren't we still using flint knives? Flint is hard, certainly harder than bronze. But it shatters easily, and it tends to shatter while you're using it. Bronze, made from copper (see right) and tin, is tougher, and if it gets blunt, then you can sharpen it. Iron ore is more common than copper and tin, but more difficult to smelt (extract the metal from the ore). Steel (iron mixed with other metals) is very hard and strong. As mankind progressed, we got better and better materials for our tools.

flint house Sandstone But what else do we use? We need somewhere to live. Nowadays, we live in brick houses, or possibly houses made of limestone. Originally, mankind lived in caves or built houses of wood. But places where suitable building stone was close by meant that we could have houses made of stone. What makes a good building stone? First, we must have a lot of it. It's no good saying you want a house built of diamond - there isn't enough! Next, it helps a lot if the quarry for the stone is close. Stone is very heavy and we don't want to transport it too far, especially if we live so long ago that we don't have any lorries or trains to transport it for us (although prehistoric man used bluestone from Wales to make Stonehenge!) In parts of East Anglia, the local building stone was flint (see left). Next the stone must be hard enough to stand up to the weather, but soft enough to cut into the pieces that you want to make the house. Sandstone is soft and easy to cut, but weathers badly (see right). Anything made of granite seems to last for ever, but it's very hard to cut. If you travel through Britain, you can see how the stone in houses varies from place to place. If every house is built of stone, it's usually because the local stone is a good building stone, such as in Stamford or Bath. Once you have built the walls, you must think about the roof! Slate is often used for roofs as it can be split easily into thin sheets.

Lapis Lazuli Talc While good building stone must be quite hard, there is a use for soft minerals, especially brightly coloured ones. Mankind has always enjoyed painting, either walls, or each other! Paints and cosmetics are pigments and some sort of liquid to hold it (such as water or oil). Originally pigments were just ground up minerals, such as lapis lazuli (see left) or red ochre. There are other uses for soft minerals. You use talc (see right) for talcum powder. You wouldn't want to spread something hard and gritty over yourself after a bath, would you?

Diamond Corundum We can also use extremely hard materials. Minerals are classified by their hardness according to the Mohr scale. Looking at this scale, it is striking that that hardest minerals are all gemstones, such as diamond (see left), rubies and sapphires. This is not an accident. Gemstones get rubbed while wearing, and soft stones will fall out of their mountings. However, these minerals are used in other ways. Diamonds are used for the best cutting equipment and corundum (see right) is used for smoothing and polishing.

Peridot Opal Gemstones are very colourful, but minerals have other optical properties. They can be transluscent like peridot (left) or glow with colours like opal, or have other strange properties like double refraction or being dichromatic. You can have yellow stripes move across tiger's eye or glints of colour appear in a sunstone or peacock blues and greens flash into sight on labradorite.

galena Pumice There are other properties than hardness or colour. You may think that minerals are heavy, and indeed, lead is heavy, so you can use it as weights, for diving. It used to be used for fishing, but unfortunately it has another property, it's poisonous! On the other hard, pumice is a rock which is so light it floats, which is useful when you lose it in the bath! The Romans used this lightness of pumice when making the Pantheon in Rome. This has a dome made of concrete. Concrete is usually made of limestone, but for the top of the dome, the Romans mixed in pumice. This made the dome much lighter, and it hasn't fallen down yet.

Clear Quartz Fireworks There are many other properties. You may be wearing a watch containing quartz (see left) because quartz vibrates in a very regular way. Certain compounds of metals produce beautiful colours for fireworks, while sulphur makes gunpowder and uranium makes nuclear weapons. Fluorite and mica has special industrial uses. If you look through the minerals in this site, you will find other properties mentioned. You can also look at elements and metals which can be extracted from minerals.