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flat black stones paving a road - basalt

A Roman road paved in basalt (This is from Trajan’s Market in Rome)

Basalt and volcanoes

Basalt (bu-SALT) is a volcanic stone – it forms from the lava that volcanoes spew out when they erupt. So it is an igneous rock. It is a very hard, black stone.

What is basalt made of?
More about igneous rocks
All our geology articles

Basalt grindstones

It makes a good stone for grinding wheat and barley and millet into flour. By the Stone Age people who lived in places in Africa and West Asia where there was basalt were already selling these grindstones to their neighbors, and even to people living pretty far away. Basalt is heavy, but people moved it around on boats, so they didn’t have to carry it themselves.

Early African ships and sailing
History of wheat
Where does barley come from?

black shiny stone basalt statue of a naked woman in an Egyptian style

Egyptian basalt statue of Cleopatra (not that Cleopatra, but an earlier one, related to her) from the Hermitage Museum in Russia

Basalt statues

By the beginning of the Bronze Age, stone carvers in Ancient Egypt also used basalt to make statues. When you polish it, basalt makes very dramatic looking shiny black statues.

Egyptian sculpture
All our ancient Egypt articles

Basalt roads

In the Roman Empire, the Romans used this hard stone for roads, because it was very hard so it would last a long time. They still used basalt for grinding stones, too. Roman traders often shipped grinding stones on sailing ships to markets all over the Mediterranean, so people could have good grinding stones even where there weren’t any volcanoes.

Roman ships and sailing
All our ancient Rome articles

A little girl standing in front of a basalt hour-glass shaped mill, on basalt pavement, with brick buildings in the background

A basalt grinding-mill at Ostia, near Rome

In the Roman Empire, people made more complicated basalt grindstones. This one, shaped like an hourglass set over a cone-shaped piece underneath, is a typical Roman grain mill.

Slavery in ancient Rome
Where do donkeys come from?

The grain mill is in a bakery, where enslaved people poured wheat or barley in the top of the hourglass (it’s mostly broken off now). Then enslaved people or donkeys pushed the top around in circles. (See the socket where you can put in a wooden beam to push with?).
The flour came out the bottom, where the little girl’s neck is. This bakery had four or five mills like this one, to make enough flour for all the bread they sold.

More about Roman food

Egyptian sculpture

Bibliography and further reading about igneous stone and and volcanoes:

Volcanoes, by Peter Francis and Clive Oppenheimer (second edition 2004).

Why is it igneous?
What is Limestone?
And what is Tufa?
What is Travertine?
What is Marble? home