Grenada

Sand grains in ancient pottery from Grenada reveal journeys between Caribbean islands.

On Carriacou, researchers cut thin sections from prehistoric pottery and examined the sand grains under a petrographic microscope. The minerals, textures and composition of the grains act like a geological signature.

When that signature was compared with local sand, some samples did not match at all. One quartz-rich group closely resembled sand from Barbados. Another group, rich in potassium feldspar, pointed towards Puerto Rico.

That means sand, or finished vessels may have travelled between islands hundreds or even more than a thousand years ago.

A few microscopic grains of sand can reveal that people and materials were moving across the Caribbean long before modern transport routes existed.