Brazilian diamonds, largely undisturbed for 4.5 billion years, provide a window into the Earth’s primordial past, says Dutch geochemist Suzette Timmerman.
Most diamonds—the hardest substance on Earth—form 150-200 kilometers below the Earth. But 99% of the diamonds from the Juina area of western Brazil formed between 410-660 kilometers below, she says.
By studying the imperfections in the diamonds, caused by helium trapped within them, and measuring the helium isotope ratios, Timmerman discovered something groundbreaking.
The trapped helium in Juina diamonds closely matches the composition of the primordial matter that originally formed our planet.
That means the Juina diamonds are older than the Moon or anything on the Earth’s surface.