EXHIBIT 99.1

ALLEGHANY CORPORATION
375 Park Avenue
New York, NY 10152

     Contact:  Robert M. Hart
     (212) 752-1356

                                                           FOR IMMEDIATE RELEASE

                  NEW YORK, N.Y. - MAY 19, 2005 - Alleghany Corporation (NYSE:
Y) today announced that it has signed a definitive agreement providing for the
sale of its world-wide industrial minerals business, World Minerals Inc., to
Imerys USA, Inc., a wholly-owned subsidiary of Imerys, S.A.

                  Under the terms of the proposed transaction, Alleghany will
receive a purchase price of $230 million in cash, subject to adjustment at
closing for certain items which are expected to result in a net purchase price
of approximately $215 million. Alleghany anticipates that the transaction will
result in a modest after-tax gain. The transaction has been approved by the
Board of Directors of Alleghany and is expected to close in approximately 6 to 8
weeks. The transaction is subject to customary closing conditions, including
antitrust approvals.

                  Weston M. Hicks, President and chief executive officer of
Alleghany, said, "We are pleased that we have reached an agreement to sell World
Minerals to one of the world's leading global minerals companies, which should
ensure that the company will prosper over the long term. With the completion of
this transaction, Alleghany will have substantial liquidity to be used
opportunistically to enhance returns to our shareholders."

                  Headquartered in Santa Barbara, California, World Minerals is
principally engaged in the mining, production and sale of two industrial
minerals, diatomite and perlite. World Minerals operates 23 plants in North
America, Latin America, Europe and China. It had about 1,600 employees at the
end of 2004.

                  In addition to the industrial minerals business conducted by
World Minerals, Alleghany is engaged through its subsidiary Alleghany Insurance
Holdings LLC (consisting of RSUI Group, Inc., Capitol Transamerica Corporation
and Darwin Professional Underwriters, Inc.) in the property and casualty
insurance business.

                  This press release contains forward-looking statements with
respect to the anticipated effects of the transaction. Actual results of the
transaction could be significantly different. Factors that could affect results
include those set forth in filings made by Alleghany with the Securities and
Exchange Commission. Although forward-looking statements help to provide
complete information about future prospects, readers should keep in mind that
forward-looking statements are much less reliable than historical information.

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