The boulders that wall the beach at Anse Source d'Argent into coves, on La Digue in the Seychelles, are pink granite you could not see over: not what mid-ocean islands are made of. Everywhere else this far out the land is coral or lava. The Seychelles are a stranded fragment of an old supercontinent, and this rock is about 750 million years old. It did not arrive as loose stones either. These boulders are bedrock, rounded where they sit: rain works into the cracks and rots the minerals until the outer layers flake off like onion skin. Corners wear fastest, so the blocks end up smooth. The beach is really a chain of small coves, each closed off by rock. You move between them by wading the shallow pools the boulders cup out of the lagoon, clear enough to watch your own feet on the sand the whole way.
The only way in is on foot or by bicycle through L'Union Estate, an old coconut-and-vanilla plantation. A sandy track runs past a colonial house, a working copra mill, and a pen of Aldabra giant tortoises heavy enough for you to lean on. The estate's vanilla was an orchid whose flowers open for barely a day and, away from Mexico, set no pods unless someone pollinated each one by hand. The method still used across the Indian Ocean was worked out in 1841 by Edmond Albius, a twelve-year-old enslaved boy on Réunion. Low tide is the best of it. The water pulls back and leaves a sheet of wet sand that reflects the boulders whole, doubling the pink granite against the sky. At high water the pools fill in and the coves shrink to a few metres of dry beach. The beach faces west, so the day ends here. The shallows go molten, the reef sharpens to a line offshore, and the granite holds its colour long after the sun is down. What you are leaning on while it does is 750 million years old.