Commodities trading giant Glencore has priced its public offering at between 480p and 580p per share, giving it a valuation nearer to $45bn than the $83bn some banking advisers had estimated.
Glencore, the world's largest commodities trader, has been a private firm since its creation 37 years ago.
Last month, Glencore announced the appointment of Simon Murray as chairman.
The float will turn executives including chief executive Ivan Glasenberg, a former coal trader, into paper billionaires.
It will be the largest London float.