Primitive Technology: Making cement out of iron bacteria

In the video, John Plant collects iron bacteria from a stream, decants it down to a mud, sun-dries it, then forms it into pots. Once dry and hardened, the pots will not dissolve in water, even though they are not fired.

I love learning things like this on Primitive Technology. I had no idea until watching this episode that you can make such a cement using nothing more than iron bacteria.