Tech: Making a stone blade

Because I used to teach students about human evolution at a large museum, I used to show them how to make basalt blades, using basalt cobbles that I collected from a South Coast beach in New South Wales, Australia. You will need to amend these details to suit your stone, which is why there are few pictures here.

NOTE: While you are banging rocks together, wear thick gardening gloves, and you (and anybody watching) must wear safety goggles and ear protection, because chips fly off and rock-banging is noisy. I did my work some distance from the audience.

The best basalt for the task is fine-grained, which seems to mean that it will always have fine bubble marks on the outside: I presume this came from lava which cooled fast and that meant being close to the surface, which meant low pressure, and that allowed bubbles to expand.

The coarser rock on the left is coarser is my anvil rock. The one in the middle appeared have been split before. Far right: a blade that could cut leather and paper, and also chop softwood.

The best stones have diagonal planes of weakness through them. Take a larger stone in your left hand (if you are right handed), hold the blade stone in your right hand as though you are going to skim it across water, and bang it down sharply on the anvil stone.

If your stone is a good one, it may still take a dozen or more blows before it shears. Small pieces may fly off, so I repeat: gloves, ear protection and safety goggles are a good idea— and stay away from other people!

This makes a crude sharp edge, which you can work further, if you wish: a common Australian Indigenous tool for improving edges is a kangaroo tooth, or you can grind the edge on a piece of sandstone. Be warned: the fresh edges will cut flesh quite easily!

Once you have tried this, and especially if you have succeeded, you will know that anybody who looks down on “Stone Age people” as ignorant savages is talking through his or her hat.

I will not reveal my source of stone, but it is only just in the Sydney Basin. Some of the best tools I have seen were made not from basalt but from quartzite. In June 2019, I got a useful blade from a piece of quartzite picked up on a mountain near Chefchaouen in Morocco.

A small fragment of quartzite, picked up on a mountain track in Morocco.

The picture above has an inset that shows you what to look for with a hand lens: this is clearly a rock that will break into sharp fragments.

There could be an interesting project in studying different stones in your locality as tool-making material, but you must wear goggles, because eyes hit by sharp rock don’t grow back.

In Europe, of course, they use (and used) flint and obsidian for this sort of work, but those stones seem to be hard to find in Australia. What can you find out about silcrete?

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