From a distance it looked like rock. Up close it looked like Superman’s Fortress of Solitude — an emerald anomaly floating in a sea of white. It sounded equally strange, fizzing through cracks in its surface as pockets of compressed air, water and ice did battle within.

What, I asked myself, is that?

It was, of course, an iceberg, but in a highly unusual state. This one had recently flipped over, revealing a pure jade underside for a brief, wondrous window of time. This is the story of how we found it.