The ratio which represents an 8% premium was higher than had been expected.
The move has been taken to defuse concerns among Xstrata investors about an easy deal between the chief executives of the two companies.
Xstrata shareholders are set to receive 2.8 shares in Glencore for each share held, reports the Financial Times.
Glencore already has a 34% stake in Xstrata and the two companies have held on-off talks over years.
Last week, Glencore approached Xstrata and was in talks over an all-share merger of equals.
The two groups, which restarted discussions in December 2011, have reached a preliminary understanding on the structure of the combined group’s top management.
Glencore Chief Executive Ivan Glasenberg and Mick Davis, the chief executives of Xstrata will make-up the combined company’s board and senior management.
