Buffett's Berkshire HathawayBy investing in American energy giant Chevron CorpMade $1.2 billion in less than 10 weeks.

In its fourth-quarter position report last month, Berkshire disclosed that it had built a position in Chevron Corp since the third quarter of last year and held a 2.5 per cent stake in the company at the end of last year, worth $4.1 billion.

As the price of crude oil rebounded, Chevron Corp's share price has risen 29% since then, and the value of Berkshire's stake has increased by $1.2 billion to $5.3 billion.

Buffett said in a recent letter to shareholders that Chevron Corp was one of his top ten heavy stocks by the end of last year.