March 6 (Reuters) - U.S. minerals and materials group, AMCOL International ACO.N , has given Paris-based Imerys IMTP.PA four working days to match a rival bid by Minerals Technologies, which AMCOL's board has deemed superior.

Minerals Technologies MTX.N raised its offer to $45.75, valuing AMCOL at $1.48 billion, on Thursday morning. This was 50 cents higher than Imerys' bid on Tuesday.

"If the revised (Minerals') proposal continues to constitute a superior proposal after the expiration of the waiting period, the company expects to terminate the Imerys agreement and enter into a binding definitive agreement with MTI," AMCOL said in a statement. ID:nPnVMvd

Minerals Technologies and Imerys are both bidding for Amcol, which has large reserves of bentonite - a key mineral used in the construction and energy industries.

AMCOL said it continues to favour a deal with Imerys.

Minerals Technologies has hiked its offer twice this week, first to $45 and now $45.75, after AMCOL accepted Imerys' sweetened takeover offer for $42.75 per share last week.

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(Reporting by Mridhula Raghavan in Bangalore; Editing by Ed Davies)

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Keywords: AMCOL IMERYS/