The Earth itself is around 4.65 billion years old, so not much older than black diamonds. Carbonados are extremely rare and have only ever been discovered in Brazil and the Central African Republic.

Carbonados are extremely rare and have only ever been discovered ... Although the precise origin of black diamonds is shrouded in mystery. Black diamonds are usually around 2.6 to 3.2 billion ...

Only known to exist in Brazil and the Central African Republic, “carbonado” black diamonds date from around 2.6 to 3.8 billion years ago and are an extremely rare natural occurrence.