aggregate
Flint
SiO2
- Also known as
- chertsilex
- Crystal system
- trigonal
- Hardness
- 7 on the Mohs scale
- Lustre
- waxy
- Colour
- Grey to black, sometimes brown, usually with a white cortex
- Where it forms
- In chalk and limestone, from the silica of dissolved sponge spicules and microfossils, reprecipitated into nodules within the sediment after burial.
- Chiefly from
- southern Englandnorthern FranceDenmarkPoland
Why it is that colour
Organic carbon and iron compounds from the sediment it formed in. The pale outer rind is weathered, chemically altered flint rather than a different material.
Safety
Safe to handle. Knapping it produces extremely sharp fragments and fine silica dust, both of which are genuine hazards, and freshly struck flakes are sharper than a surgical blade.
Where it comes from
Abundant across the chalk belts of northern Europe. Neolithic flint mines at Grimes Graves in Norfolk and Spiennes in Belgium are UNESCO-recognised and among the earliest industrial sites known.
Historical use
The single most consequential stone in human history. Its conchoidal fracture — it breaks in smooth curved surfaces rather than along planes — means it can be worked to a controlled edge, and stone tool industries from the Palaeolithic onward depend on it. Later it struck sparks against steel for fire and for firearms, which is why the flintlock is named for it, and why flint mining continued industrially into the nineteenth century.
Recorded as history and attributed where possible. That a stone was used for something establishes that people used it, not that it worked.
Worth knowing
Flint is in this collection precisely because nothing metaphysical is attributed to it. It is the control case: a silica variety, chemically almost identical to the stones on either side of it in this list, which the modern trade has no use for because it is grey, common and unglamorous.
By any measure that is not aesthetic, it is the most important stone there is. Hominins were working it two and a half million years before anyone thought of putting a crystal on a windowsill, and the reason is a purely mechanical property: it has no cleavage planes, so it fractures in predictable curved surfaces and a skilled knapper can control exactly where the edge goes. Obsidian does the same thing better but is confined to volcanic regions. Flint is in the chalk under half of northern Europe.
The archaeologists' lithotheques that give this collection its name are, more than anything else, collections of flint.
Identity checked against IMA-CNMNC master list, June 2025.