Here Is a 4.4 Billion-Year-Old Australian Gemstone
At the Sydney Morning Herald:
Scientists using two different age-determining techniques have shown that a tiny zircon crystal found on a sheep ranch in Western Australia is the oldest known piece of our planet, dating to 4.4 billion years ago.
[…] To put that age in perspective, the Earth itself formed 4.5 billion years ago as a ball of molten rock, meaning that its crust formed relatively soon thereafter, 100 million years later. The age of the crystal also means that the crust appeared just 160 million years after the very formation of the solar system.
This time period is the Hadean eon, named for “hellish conditions including meteorite bombardment and an initially molten surface.” But this tiny little crystal (“twice the diameter of a human hair”) suggests that the shift to ocean-sustainable temperatures may have occurred earlier, and we might have had what a University of Wisconsin geologist named Professor Valley calls a “cool early earth.” [SMH]