(Reuters) - British specialty chemicals firm Elementis <ELM.L> said on Thursday it had rejected an all-cash buyout offer from larger rival Minerals Technologies <MTX.N>, as the 621.5 million pounds valuation for the company was too low.
Shares in Elementis rose 7.7% to 105.5 pence by 1028 GMT, below the 107 pence per share offer.
Elementis' board unanimously rejected the proposal, saying it significantly undervalued the company and its future prospects.
Founded in 1844, the British company makes additives that go into products in the consumer and industrial markets, including personal care, coatings, chromium, energy and talc.
It said last month earlier it had a robust order book for November and that it was on track to deliver a significant reduction in net debt by the end of the year.
New York-based Mineral Technologies, which approached Elementis earlier in the month, said it was currently considering its position on a possible proposal for the British firm.
The proposal highlighted the fact shares in Elementis, which have fallen around 47% so far this year, have been cheap, according to Jefferies analysts.
The offer represented a premium of 31% to Elementis' closing share price of 81.70 pence on Nov. 4.
Elementis has 580.8 million shares in issue, according to its website.
(Reporting by Samantha Machado and Tanishaa Nadkar in Bengaluru; Editing by Saumyadeb Chakrabarty)