The transaction would create the world’s No.2 platinum producer as Lonmin is the world’s third-largest while Sibanye-Stillwater is the fourth.
Sibanye-Stillwater Mining News
The company also expects to halve the amount of job cuts previously announced in the gold division to around 3,000.
A rise in producer profits is likely to provoke higher wage demands from labour unions including the militant AMCU.
The Association of Mineworkers and Construction Union (AMCU) lodged its appeal in protest against job cuts related to the deal.
The London-based company, which operates in South Africa, said total platinum production tumbled 10.3% to 276,020 ounces for the six months ended March 31.
Despite its fraught relationship with with the Association of Mineworkers and Construction Union, experts say recent developments play in favour of the company.
South Africa's labour registrar said in the government gazette this week that he intended to cancel the registration of AMCU.
Sibanye-Stillwater has revised its offer for Lonmin, with new terms that gave a valuation for the struggling platinum miner that was about $77m less than originally proposed.
The company, South Africa's largest gold producer, has run up losses of about 1.6 billion rand ($114 million) and about 110,000 ounces of missed gold output because of the labour action.
This is the second major step by the company this week to build up cash as it faces a drawn-out labor dispute.
The precious metals producer is looking into opportunities in gold and the battery metals sectors.
Lonmin Plc has been cutting spending to conserve cash and retain a positive balance sheet required by conditions of South Africa-based Sibanye's offer.
South Africa's labour court has ruled that the extension of a wage agreement to cover all gold unions and non-unionised employees of Sibanye-Stillwater is valid and lawful.
AMCU has been on strike at Sibanye-Stillwater's gold operations since mid-November in a pay dispute.
Foreign platinum and diamond miners have been restricted to only 49 percent ownership of their Zimbabwe operations by the black economic empowerment law.
"We will further investigate tax planning alternatives to minimise this additional deferred tax," Sibanye's statement said.
South Africa intends to play its role as part of the global effort to reduce global greenhouse emissions.
AMCU has been on strike since mid-November over a wage dispute - after losses at some of its mines last year.
Sibanye-Stillwater said it had entered into talks with stakeholders on restructuring its gold operations following financial losses at the Beatrix 1 and Driefontein 2,6,7,8 shafts during 2018.
Gold producers in Africa's most industrialised economy, have seen profits squeezed by rising costs, labour unrest and declining grades.
The new strike would begin on Jan. 22 and involve around 12,500 of its members.
Since the union downed tools at Sibanye's gold operations in mid-November, four employees have been killed during strike-related violence.
The company's gold output in 2018 will be lower than forecast as almost half of the employees stopped working since mid-November in a wage strike.
AMCU's strike is a protected strike and the AMCU members' constitutional right to strike remains protected.
The all-share deal is likely to lead to more than 10,000 layoffs.