De Beers

Read the two articles. What theories from this quarter best describes what is occuring or has occured(use monopoly)? Explain how the theories work and how they can be observed.
https://www.paulzimnisky.com/a-brief-history-of-de-beers
https://www.businessinsider.com/history-of-de-beers-2011-12#by-the-time-rhodes-died-in-1902-de-beers-controlled-90-of-the-worlds-rough-diamond-production-and-distribution-but-it-was-ernest-oppenheimer-who-made-the-company-an-empire-4