How rocks are used
Whenever you walk on the ground you are walking over rock. This rock forms a layer under the soil. It may be sandstone, chalk, limestone or granite. It all depends where you are. If you have crossed a road today, then you will most probably have walked over basalt. This is a very hard rock, which formed from lava that escaped from a volcano. Basalt is used to make foundations for roads because it is very strong. It does not crumble when thirty tonne trucks are driven over it. When you stood on the kerb you may have been standing on a piece of granite. This rock is used to make some kerbstones because it is very tough and can take the knocks from wheels and feet without breaking up.

Rocks were one of the first materials that people used. In fact, the period when people used rocks for many different things is called the Stone Age. It ended about seven thousand years ago when people began to use metal for some items such as knives and axes instead of rocks. However, rocks continued to be an important material. In many places people collected up small rocks to build walls for their homes. Later, holes were dug in the ground to take out more rock. These holes grew in size and became quarries. The rocks taken from the quarries were used to make roads, homes and buildings of every kind, from churches and town halls to mills and factories.

Today, brick and concrete are used for making most buildings but many stone buildings remain and are still in use. Most of the stone that is used in building today is used to make buildings look attractive or for decoration. For example, polished granite makes a fine, shiny entrance to a building such as a new library while marble is used to make statues for parks and town centres.

What kind of stone did Stone Age people use?
The most widely used stone was flint. This stone is found in chalk. It is a black stone that can be carefully broken to give a very sharp cutting edge for knives, axes and arrowheads. Flint was also used to make scrapers to clean the flesh off animal skins. In some places, a kind of glass-like rock called obsidian was used instead of flint. Sometimes granite was used to make heavy hand axes.

Was flint used after the Stone Age?
Yes. Flint was used in some places such as Norfolk in England to build churches and houses. It was used to make a glaze for pottery in the eighteenth century and was used in flintlock guns. In a flintlock gun a piece of flint is struck by a piece of steel when the trigger is pulled. This makes a spark. There is a substance in the gun called a charge. The spark makes it explode and shoot a bullet out of the gun barrel. A flint was also used in a tinderbox. In this container was a piece of flint, a piece of steel and some pieces of very dry wood called tinder. When the steel was struck on the flint a spark was made. If the spark reached the tinder close by the tinder would burst into flame. It could then be used to light a fire. When matches were invented tinderboxes were no longer used. Flint is still used today in the making of some kinds of concrete.

Did people ever live in caves?
Yes, they did. So in a way this is another use for rock. One advantage of living in a cave is that the temperature varies much less than outside and there are never freezing conditions. In Nottingham in England there are many caves and they stay at a temperature of 12°C. all year round. In the past these caves were used in the brewing of beer and the tanning of leather. In other places caves have been used for the storage of wine. In Turkey the ash from an extinct volcano formed a soft rock called tuff. About six thousand years ago people made their homes in caves in the rock. In time they cut deeper into the rock and made an underground city where up to 20,000 people may have lived. People continued to live in these caves until the twentieth century.

Did Stone Age people use stone for building?
Yes. The first buildings were probably just a wall of stones to make a windbreak. From this type of simple shelter stone huts were made. These had dry stone walls and inside flat stones were used to make the sides of beds and even cupboards and boxes. The huys were circular or rectangular. The roofs were made from branches covered with thatch or turf.

What were the first quarries like?
The first quarries were cliff faces. These expanses of rock are exposed naturally as a hillside wears away. People selected rocks that had fallen off the cliff face. Later, quarries were made by digging in the ground. First the soil and roots were removed to expose the rock below. Then the rock was cut out of the ground.

How was rock cut out?
A line of wedges was tapped into the rock. These were then hit with a heavy hammer and the rock cracked open. When the rocks were removed from the ground, they were cut up into smaller pieces. String and sand were then used to cut up rocks. The sand was placed in a groove in the rock and the string was rubbed to and fro in it. Later steel saws and sand were used. Today explosives are used to blast out the rock in a quarry but saws are still used to cut up rocks.

Are stones always stuck together with mortar to make walls?
No. The first stone buildings had dry stone walls. The stones were chosen so that they could fit together firmly. Dry stone walls were used in many places to mark out fields and stop livestock roaming freely. Many field walls are still in place and in use today. When mortar was invented it was used to stick stones together. The stones did not have to be carefully chosen because they did not need to fit as tightly as in a dry stone wall. The mortar filled the gaps between them. In addition to making a stronger wall, the mortar also made the wall windproof.