China clay workers in Cornwall are threatening to take industrial action over plans by Imerys to axe up to 700 jobs.
Imerys is the largest employer in Cornwall with about 2000 workers
Two mass meetings of union members voted unanimously to take action and the unions are also planning a protest march in St Austell.
Imerys blames high energy prices, a weak dollar and strong overseas competition for the cuts.
Union members are angry over the pay-off terms put forward by Imerys.
Imerys is to close one of its seven china clay pits in the St Austell area.
One refinery and two drying units will also be closed in Cornwall and a pit at Lee Moor, north of Plymouth in Devon, will also close, along with the refinery and drying unit.
China clay, or kaolin is used to whiten and give a glossy coating to paper, but Imerys is transferring some of its production to Brazil.
The Transport and General Workers Union (T&G) claims payments for long-serving staff will average about £13,000, but Imerys insists the figure could be nearer £18,000.
French firm Imerys employs about 2,000 staff in the region and is Cornwall's largest private employer.
Senior shop steward Tony Lobb, who has been with Imerys for 30 years, said he would be getting £15-17,000 redundancy payment.
"Ten years ago someone like me would have gone out with at least £30-£35,000," he said.
"I have been loyal, but they are not going to reward me with the amounts of money they should be. It's putrid."
Jenny Formby, national secretary of the T&G, said that unions in France were also being consulted on industrial action over the lay-offs.
She said: "Our members are desperate and the company is not listening."
Ashley Shopland, director of Imerys, said there had been eight formal consultations with the unions, jobs losses had been reduced by 25% since they were first announced and an extra £1m had been offered in redundancy payments.
He said: "This is a time for cool heads.
"To create more disruption for a company that is already struggling in financial terms can only put in jeopardy the future sustainability of the business and those jobs we wish to retain."