Sea Ice: Ancient Oceans Birthed Diamonds

Diamonds can form with the help of ancient saltwater, say researchers who have identified the gems that crystallized with the help of oceanic crust dating back as far as 200 million years ago. Scientists think the jewels usually form 90 to 150 miles (140 to 250 kilometers) below Earth's surface, in the planet's mantle layer, which is sandwiched between Earth's crust and core. The deepest of these precious stones have come from 430 miles (700 km) below Earth's surface.