Geopolymers: the theory that the pyramids were cast, not carved

Geopolymers: when stone is kneaded instead of carved

What if those walls with joints so tight a razor blade can't fit between the blocks weren't carved at all, but poured into a mould? The question has been circulating on the fringes of archaeology for decades and has eventually crystallised into a theory with a name of its own: geopolymers, in other words, artificial stone made on site from aggregates, alkalis and water. The hypothesis, championed by enthusiasts and by the chemist Joseph Davidovits, holds that much of the world's megalithic construction — from Sacsayhuamán to Puma Punku, via Giza — cannot be explained with copper chisels and ropes, but with formwork and basic chemistry.

The French chemist Joseph Davidovits, of the Geopolymer Institute, is the most frequently cited reference. His thesis: the blocks of the Great Pyramid would have been created on site by mixing dissolved limestone, natron and other components, and pouring them into wooden moulds. No quarries miles away, no impossible ramps. For Tiwanaku and Puma Punku he proposes two recipes: sandstone with natron, and volcanic rock with acidic plant extracts and guano. The dating he works with places that civilisation between 600 BC and 900 AD.

The impossible joint and the awkward protrusion

The visual argument is compelling. Curved walls with polygonal blocks fitted to the millimetre, bulging inner faces, protrusions at the bottom edge of many stones. That last detail has baffled observers: why leave a knob on the underside of a block if you carved it? One explanation doing the rounds is that it served as a drain for the excess water from the mix, which would otherwise ruin the setting. Another points to a net or biodegradable mesh that would have left that grid-like mark visible on some blocks at Giza.

The irregularity of the blocks, which at first glance seems self-contradictory — if you're making stone, you'd make it uniform — also has an answer. In seismic zones, polygonal guasonry with curved inner faces distributes stress better than a stack of homogeneous bricks. And there lies the detail that has tipped the scales for some: those bulging inner faces can't be seen, they don't show, they aren't decorative. They only make structural sense.

Why hasn't it been replicated with modern technology?

Here comes the resident sceptic. Granite is not concrete: its crystals of mica, quartz and feldspar interlock with no gaps or filler material, having crystallised in different phases. Reproducing that with a mix at room temperature is another matter entirely. Modern concrete is distinguishable from natural stone even by a child, and no one has yet produced a laboratory-made piece that could fool a geologist. It is the strongest objection, and it remains unresolved.

Added to that is the problem of the recipe. How on earth would anyone discover that a mixture of two plants, with their acidic kick, softens rock? Some point to animal observation: certain birds use a similar paste to bore into living rock. Others invoke the Andean legend of the priest who rediscovered the method, chewing coca to endure the effort and using another plant to soften the granite.

The Osireion, Dendera and the underlying resonance

The catalogue keeps growing. The Osireion at Abydos, with its water table encroaching on the structure, bears an uncomfortable resemblance to Peruvian stonework. In the Temple of Hathor at Dendera, the steps show shapes that don't match mechanical wear: they look like mix that set badly. And at Abu Gorab, the circular alabaster basins of Niuserre's sun temple — some 4,500 years old — look like serial-produced pieces straight out of a mould. What they were used for is another story.

Along the way appears the forbidden word: resonance. Chambers such as the Treasury of Atreus at Mycenae, with its conical vault and colossal lintel, work acoustically like boxes. And stone has piezoelectric properties. From there to imagining temples as machines is a leap, but the can of worms is open.

The closing note is ironic: for centuries we were told that those people hammered out by hand what today would take sweat even with precision machinery. If it turns out they were kneading it instead, someone will have to rewrite quite a few books. And collect, while they're at it, for the lost faith.