All about diamonds
It was known that kimberlite, which often contains diamonds, can rise more quickly near the surface, but its speed at great depths was unclear.
And now, Masayuki Nishi and colleagues at Kyushu University in Fukuoka, Japan, have used the mineral garnet as a speedometer.
Garnet inclusions that form inside diamond are stable at depths of between 400 and 700 kilometres, but partially degrade at lower pressures and temperatures.
The researchers synthesised garnet in heated, pressurised containers and measured how fast it degraded as the temperature and pressure were lowered, simulating ascent through Earth's mantle.
And the rate of decay suggested that for a garnet-infused diamond to reach the surface it must take between hours and days to travel from a depth of 400 km.
- Diamond infused magma travel to the surface of the earth from deep within the planet at a blistering 60 kilometres per hour.