Not all diamonds found on Earth originated from Earth. Some researchers found primitive interstellar meteorites which contains carbon in a form of diamond called carbonado; after studying them, it turned out to be around 3 billion years ago stones; they say that it was caused by asteroids which hit the world specially in South America and Africa. These diamonds have formed in the interstellar environment. but till 2008, no final study was submitted on how the carbonado diamonds were originated from.
Other natural high-Pressure conditions might form diamonds as well. Very small diamonds of micrometer and nanometer sizes, known as microdiamonds or nanodiamonds respectively, have been found in meteorite impact craters. Diamond might be formed in a shock zone of high pressure and temperature. Impact-type microdiamonds can be used as an indicator of ancient impact craters.
” Popigai crater ” the area that is now known as the Tamyr Peninsula of northern Siberia, Russia may have the world’s largest diamond deposit, estimated at trillions of carats, and formed by an asteroid impact. The explosion produced a 100 kilometer-wide impact crater with a rim of deformed rock up to 20 kilometers wide. We now know this feature as “Popigai Crater” or “Popigai Astroblem”, the seventh largest impact crater that has been identified on Earth.