Buckingham Palace will host a diamond exhibition in August and September, in honor of Queen Elizabeth's Diamond Jubilee this year, titled ''Diamonds: A Jubilee Celebration.'' The event will show various ways in which diamonds have been used and worn by British monarchs over the past two centuries. The exhibition also includes an unprecedented number of the Queen's personal jewels that have been inherited or acquired during her 60-year reign, such as the diamond tiara she frequently wears.