Fool’s Gold

We’re walking the coast of Westray when we see large chunks of what look like rusty metal embedded in the rocks. There’s a trail of nuggets of them along the face of these rocks on the shore at Stancro. Can you see the chunky rusty-brown patches?

We look closer and can see their irregular shapes and the rusty iron look:

It’s iron pyrite, or Fool’s Gold. It’s proof that 380 million years ago the bottom of Lake Orcadie lacked oxygen, and was a so-called anaerobic environment. That’s the only possible reason the sulphur in it wouldn’t have bonded with oxygen.

380 million years later, the pyrite is finally reacting with oxygen and water to form sulphur dioxide gas and sulphuric acid, and is leaving that rusty iron sulphate behind. It’s been a long time coming, but the sulphur finally found a better, more stable, binding partner.