Minerals Technologies Inc (MTX.N) raised its offer to buy Amcol International Corp ACO.N to about $1.38 billion.
The offer of $42.50 per share represents a 7 percent discount to Amcol's Monday close.
U.S.-based Minerals Technologies and France's Imerys (IMTP.PA) are both bidding for Amcol, a company that owns large reserves of bentonite, a key mineral used in construction and energy industries.
Minerals Technologies had offered to buy Amcol for $42 per share on February 14, topping an offer of $41 per share from Imerys. Three days later Imerys said it remained committed to Amcol $41 per share.
(Reporting by Swetha Gopinath in Bangalore; Editing by Saumyadeb Chakrabarty)