Around lunchtime on March 1st, 2024, Patrick Roycroft, geology curator at the National Museum of Ireland, was given a piece of mineral, about the size of a Creme Egg, by a seven-year-old boy called Ben O’Driscoll. Just a few weeks earlier, in mid-February, Ben had returned home after soccer practice one Saturday morning and had decided to explore a field near his home in Rockforest East, near Mallow in Co Cork.
He knew from his grandfather’s stories that something unusual might lie beneath the fields and he was encouraged to go searching. That day, as he ran out to a freshly ploughed field, Ben spotted something in the mud. When he showed his mother, Melanie, what he’d found, she sensed he’d struck it lucky. She got in touch with Roycroft, packed the family into the car and drove up to Dublin through the snow, with the small, pearly stone in tow to find out more.
Roycroft knew exactly what he was looking for. Within seconds, he realised what he had in his palm was genuine: a true cotterite, one of the rarest forms of quartz in the world. It had a very characteristic optical effect – a silvery lustre – which is not seen in any other quartz. What Ben had found was the first discovery of cotterite in 150 years.
To label cotterite as “rare” – implying it exists in small numbers, but might still turn up somewhere, some time again – is almost misleading. There are about three dozen known authentic cotterite specimens, which are held by museums in Cork, Dublin, London and even the Smithsonian in Washington. They were all found within a few months of each other and derive from a single horizontal vein of calcite, quartz and ferruginous mud cut through carboniferous limestone in Rockforest. It was formed in a single geological event under conditions so specific that, as far as scientists know, they have never been repeated anywhere else in the world since.
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