Liz Harper

speaker

123 appearances 1 recordings 1 series first heard Jul 2026 last heard 30 Jul

Liz Harper’s voice in public audio — every appearance, attributed to the second.

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Recordings per month over the last 12 months — 1 in all, peaking in Jul 2026 with 1.

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In Our Time · Seashells · 30 Jul 2026 podcast

You can get it straight from the seawater, from dissolved calcium.

and carbonate, which comes from dissolved carbon dioxide from the atmosphere.

So very easy building blocks, but it turns out actually that those minerals are pretty rubbish things to make armour out of.

So it's very weak, it's very soft, and it has a very bad habit of dissolving in acidic waters.

So it seems like a really unpromising stuff.

But the mollusks actually are much more ingenious than just laying down that mineral.

So it's a biocomposite they make.

So the vast majority of it is calcium carbonate, but it's got a small proportion of organic material in it.

That is magic, and it transforms the properties of this rather rubbish shell material.

Yes, and they are usually laying down those organics in the first place, and that then controls and helps the calcium carbonate lay down, in particular orientations and morphologies.

They have the most beautiful, intricate microstructures, which have various properties that the mollusks then use to their advantage.

But that laying down the calcium carbonate goes on below an organic sheet, a thing called the periostricum, that perhaps we might talk about again.

But that organic layer on the outside of the shell is the first bit of the shell to be laid down.

And that's the template onto which this magic biocomposite can then be laid and controlled.

So it's very highly controlled by the animal.

It's not something that happens by accident.

Yes, absolutely.

Well, for many, so it varies quite a lot.

So things like a mussel, if you think about seeing a mussel on the seashore, it very often has a thin brown layer on the outside that eventually wears off.

That might be several tens, maybe several hundreds of microns thick.

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