Two teams of U.S. researchers have found that carbonados — or black diamonds-com from outer space. Helped with funds from the National Science Foundation (NSF), they discovered nitrogen and hydrogen in these porous black diamonds found only in Brazil and the Central African Republic. And these elements are not found in conventional diamonds extracted from mines from volcanic rocks. They think these carbonados were part of asteroids which landed on Earth about 3 billion years ago.

This research was done by jozsef Garai and stephen Haggerty of Florida International University, along with Case Western Reserve University researchers Sandeep Rekhi and Mark Chance. For this project, they used the infrared synchrotron radiation at Brookhaven National Laboratory and a technology named Fourier transform infrared spectroscopy or FTIR (Link to wikipedia)

So even the NSF agreed that these diamonds come from far beyond the Earth. Here is an explanation.