Shares in British refractories maker Vesuvius rose as much as 31% on Tuesday after it said it was assessing a £1.37 billion ($1.81 billion) cash-and-stock takeover proposal from Austria-based RHI Magnesita. The latest proposal values Vesuvius at 551 pence per share, a 47% premium to Monday's close, and follows several approaches rejected by Vesuvius over the past year. The stock was last up 23% at 461 pence, while RHI Magnesita's London-listed shares fell 3%. The proposal comprises 470 pence in cash and 0.28 new RHI Magnesita shares for every 10 Vesuvius shares, based on RHI Magnesita's one-month volume-weighted average share price on Aug. 27. Vesuvius is reviewing the terms and execution risks with financial and legal advisers and has warned that no firm offer is certain. If completed, the deal would give Vesuvius shareholders about 7.1 million new RHI Magnesita shares, or roughly 13% of the enlarged company. Cevian Capital, Vesuvius's largest shareholder, supports the proposed terms. Both companies make refractory materials used to line furnaces, ladles and vessels in high-temperature industries including steelmaking. Under Britain's Takeover Code, RHI Magnesita must by 5 p.m. London time on Oct. 27 announce a firm intention to bid or say it does not intend to do so, unless the deadline is extended.