Stone Tools

Most stone tools are pieces of rock broken in a controlled way to give a sharp edge for cutting, scraping or chopping. They are the oldest known technology: the earliest date back about 3.3 million years, and people still made some into the twentieth century.

What it is

Any stone used as a tool counts, from a plain hammerstone to a grinding slab, but most were shaped by breaking off flakes to get a cutting edge or a point. The simplest is a sharp flake knocked off a pebble and used at once to cut meat or strip a branch. The most refined, such as a thin spear point or a polished axe, took hours of skilled work.

For most of human history, stone was the main hard material available. Wood, bone, hide and fibre were worked with stone edges, and stone tools last almost forever, so they are also the main record archaeologists have of how early humans lived.

How it works

Good tool stones are hard, brittle and fine-grained, with no internal grain: flint, chert, obsidian (volcanic glass) and some quartzites. When such a stone is struck near an edge, the blow sends a cone-shaped crack through it, the same shape a pellet makes in a window pane. The crack curves out to the surface and frees a flake. This shell-like break is called conchoidal fracture, and it gives very thin, sharp edges.

Pressure flaking: an antler tine pushes small flakes off the edge while the leather protects the palm.

The knapper strikes the core on a flat surface called the striking platform, close to its edge. Where the platform meets the face of the core, the angle must be less than 90 degrees, or the blow only crushes the edge. The detached flake carries the marks of the blow: a rounded swelling just below the point of impact, the bulb of percussion, and fine ripples spreading away from it. The core keeps the matching hollow scar, and that scar can serve as the platform for the next blow.

Three techniques control the result. A hard hammer, usually a quartzite cobble, removes large, thick flakes. A soft hammer of antler, bone or hardwood removes longer, thinner flakes and is used to thin and shape a tool. Pressure flaking presses an antler tip against the edge until a small flake springs off; it gives the final shape and a straight, sharp edge.

How to build

Knapping is learned by practice, and the first hours produce mostly broken stone. You need nodules of flint or chert, or chunks of obsidian or thick bottle glass; two or three hammerstones of different weights; an antler billet and an antler tine; a thick leather pad; safety glasses; leather gloves; and a tarpaulin to catch the waste.

Choose the stone. Look for a nodule without cracks, holes or coarse patches. Tap it with a small pebble: a clear ring means sound stone, a dull note means hidden flaws.

Find a platform. Look for an edge where two surfaces meet at less than 90 degrees. Strike a little way in from that edge, a few millimetres for a thin flake and more for a thick one, with a short, firm blow that follows through outwards, away from the core. Rest the core on the pad on your thigh, never in your bare palm.

Make a flake tool. A single good flake is already a knife. Use it as it is, or trim its back with small blows to make it easier to hold.

Shape a hand axe. Work round the edge of a flat nodule, taking flakes alternately from one face and the other so the edge becomes a wavy line in the middle of the piece. Switch to the antler billet to thin the faces. Before each blow, grind the edge lightly with a coarse stone so it does not crush.

Finish by pressure. Hold the piece on the pad, press the antler tine down and inwards on the edge, and remove small flakes one after another to straighten and sharpen it.

Safety. Fresh flakes are sharper than a razor and fly off fast. Always wear safety glasses, and protect your hands and thighs with leather. Work outdoors or in a well-ventilated space and do not breathe the fine dust: flint and chert are silica, and years of dust cause silicosis, which killed many professional gunflint knappers. Gather the waste on the tarpaulin, dampen dust instead of sweeping it dry, and put sharp flakes in a closed tin or bucket. Keep children and animals away from the work area.

History and evolution

Oldowan tools: a cobble with a jagged edge, the sharp flakes struck from it and the hammerstone.

The oldest known stone tools come from Lomekwi 3, west of Lake Turkana in Kenya. They are about 3.3 million years old, older than the earliest known fossils of the genus Homo. The team found 149 cores, flakes, hammerstones and possible anvils, made with simple techniques close to pounding. Who made them is unknown; Kenyanthropus and Australopithecus lived in the region at the time.

Oldowan tools appear at several East African sites from about 2.6 million years ago, and perhaps 2.9 million years ago at Nyayanga in Kenya: cobbles with a few flakes removed, the sharp flakes themselves and hammerstones. Around 1.7 million years ago, in East Africa, the first widely accepted hand axes appear, large tools shaped on both faces into a teardrop with a long cutting edge. People went on making them for more than a million years, across Africa, Europe and Asia.

In the Neolithic, axe heads were ground and polished on sandstone to make them tougher.

Later toolmakers learned to prepare a core so that one blow would release a flake of planned shape. By about 200,000 years ago, points were fixed to wooden shafts as spears, and stone awls and scrapers were used on hides and wood. In Europe and western Asia, between about 50,000 and 10,000 years ago, long thin blades became the standard blank. Microliths, small blade segments set in rows into handles and arrows, appear in southern Africa about 71,000 years ago and became common in many regions near the end of the last Ice Age.

Farmers of the Neolithic, from about 10,000 BCE, ground and polished stone axes to clear forest. Metal replaced stone slowly and never completely. Gunflints for flintlock guns were knapped at Brandon, in England, into the twentieth century, and obsidian blades are still used for some delicate surgery because their edges are finer than those of steel scalpels.