Evidence of a drowned "microcontinent" has been found in sand grains from the beaches of a small Indian Ocean island, scientists say.

A well-known tourist destination, Mauritius (map) is located about 1,200 miles (2,000 kilometers) off the coast of Africa, east of Madagascar. Scientists think the tiny island formed some nine million years ago from cooling lava spewed by undersea volcanoes.

But recently, researchers have found sand grains on Mauritius that contain fragments of the mineral zircon that are far older than the island, between 660 million and about 2 billion years old....