Gold and platinum shouldn't be rare on Earth—they shouldn't be here at all. Or at least, they shouldn't be in Earth's crust. These elements, along with iridium and similar metals, love iron, and thus they were sucked into our planet's molten iron core soon after Earth formed. So where did all of the material for our fancy jewelry come from? According to high-precision measurements of two isotopes, or atomic variants, of tungsten in 4-billion-old rocks from Greenland published online today in Nature, precious-metal-bearing meteorites struck Earth  around this time, coating the planet in a veneer containing gold, platinum, and other elements long after their native counterparts had disappeared into the planet's core. Proof positive that your bling really is out of this world.
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