Gina Rinehart, 57, is the richest person in Australia and predicted to become the wealthiest in the world.
Her fortune has more than doubled to A$10.3 billion (£6.8 billion) in the past year because of a commodities boom.
She is on course to overtake Carlos Slim, the Mexican magnate worth £46 billion, and the Microsoft chairman Bill Gates, who is worth £35 billion, Citigroup has estimated.
The financial group calculates that three coal and iron ore projects she is developing will lead her to overtake the men mainly because she owns her companies outright and has no shareholders.
“If Rinehart was a company listed on the [Australia Stock Exchange] and valued using the same 11-times price-to-earnings ratio as her partner, Rio Tinto, she would be worth US$30 billion (£19 billion), putting her in the top ten of the Forbes rich list, said SmartCompany, an Australian business website.
“It is possible to see Rinehart’s portfolio of coal and iron ore production spinning off annual profits approaching US$10 billion,” giving her a “personal net worth valuation of more than US$100 billion,” it added.
Ms Rinehart avoids publicity and is barely known outside of the business community. In 1952 her father, Lang Hancock, discovered the world’s largest iron ore deposit in Australia’s Pilbara region.
She married twice. Her second husband was Frank Rinehart, an American lawyer, who died in 1990.
The world's wealthiest woman is Christy Walton, the widow of John Walton, the Wal-Mart heir, who is worth $26.5bn.
French insurer Axa and Australia's AMP have launched one of Asia's biggest unsolicited takeover bids of the year, tabling a joint A$11bn (US$10.2bn) offer for Axa's majority-owned