For centuries, researchers have puzzled over how oysters grow stunningly symmetrical, perfectly round pearls around irregularly shaped grains of sand or bits of debris. Now a team has shown that ...

Of 100 oysters, only seven or eight will produce a coveted round pearl. And just one or two will have the smooth surface, size, colour and lustre to make them top-quality specimens.

Not all pearls are round, but many are, and these are the most prized. But given that the creation of a pearl happens within the locked-tight shell of a living creature, we don’t really know ...