The gift comes just days after Mrs Duffield threatened to withdraw a pounds 5.5m gift from her personal fortune to the Royal Opera House because of the continuing crisis there.
Mrs Duffield refused to answer any questions yesterday about the ROH, where she is deputy chairman, but relations between herself and the chairman, Sir Colin Southgate, are known to be strained.
Last night, the crisis at the ROH continued, with dancers from the Royal Ballet indicating that they would reject new contracts offering them reduced pay and conditions.
Sir Colin has said he would make all staff who reject the new contracts redundant next week. The ROH board meets next Wednesday.
As chairman of the ROH trust, Mrs Duffield has squeezed pledges of pounds 68m from supporters for her targeted pounds 90m toward the rebuilding of Covent Garden.
Yesterday, Mrs Duffield pledged cash from the Clore Foundation and Vivien Duffield Foundation to pay for education centres at the new Tate Gallery at Bankside, the British Museum and the Natural History Museum. Of that, pounds 1m will go toward providing small grants to local and regional museums over the next five years.
For the Tate and British Museum, the pounds 2.5m Clore Centres for Education will be part of the new building developments due to open in 2000.
At the Natural History Museum, the pounds 1m donation will fund the transformation of the Discovery Centre into a new hands-on activity area called "Investigate", with computer workstations and internet links for any "virtual visitors".
Mrs Duffield, who is chairman of the two foundations, stressed the importance of private donations like the ones she has invested for the past 15 years. She said that while governments "come and go", private funders had to be permanent fixtures.
"We're not here today to talk about the Royal Opera House," she said at a press conference to announce the donation. "For one day at least, I propose we declare a moratorium on doing so."
The British Museum's new education centre will be home to a programme of lectures, films and videos, as well as courses, conferences and performances.
It will include two lecture theatres, a foyer and an exhibition area, as well as multi-purpose areas and an artists' studio.
At the Bankside Tate, there will be a cluster of three educational areas comprising a main centre, an auditorium and an activity room.
The Natural History Museum project will, along with the development of "Investigate", help plan and implement educational events throughout the building's galleries.
The value of individual grants available for museums around the country will range from pounds 2,000 to pounds 25,000.