Scientists dated the impact by measuring the decay of uranium in zircon crystals in the rock.
On the other hand, nepheline syenite gneiss contains abundant and large zircon crystals.
The oldest, a zircon crystal from Australia, is nearly 4.3 billion years old.
Zirconium is one of the main components of zircon crystals, currently the oldest known minerals in the earth's crust.
In the rocks, the scientists found zircon crystals as old as 4.28 billion years.
More recently, Dr. Valley developed new techniques to analyze the oxygen within zircon crystals.
A second team of scientists dated other zircon crystals taken from the same site in 1999, finding one crystal 4.3 billion years old.
A zircon crystal is an example of an elongated square bipyramid.
The Earth is a little over 4.5 billion years old, its oldest materials being 4.3 billion-year-old zircon crystals.
The remarkable precision is possible because the fossils were sandwiched between lava flows that could be precisely dated from embedded zircon crystals.
