The Financial Times just published an excellent article about Glencore, its origin and its future. The King of Oil – The Secret Lives of Marc Rich was an important source and is quoted in the article:

Amid such profound changes, Glencore started to plot a new future. Such plans will move the group further from its origins under Marc Rich, an oil trader who founded the business under the name of Marc Rich + Co in 1974, and sold to management in 1993. According to Daniel Ammann’s book, The Secret Lives of Marc Rich, the founder – who made a lot of money from deals with countries shunned by others, such as apartheid South Africa and Iran – sold the company to management for about $600m, a figure Mr Rich said was not far from reality.

Source: http://www.ft.com/cms/s/0/70b00eb2-8ac1-11df-8e17-00144feab49a.html