More than 360 people have accepted voluntary redundancy as part of the restructuring of a china clay firm.
Imerys is the largest employer in Cornwall with about 2,000 workers
Imerys is cutting more than 600 jobs in Devon and Cornwall because it is moving its paper coating operations to Brazil where costs are lower.
Ashley Shopland, operations director for Imerys, said he was pleased that so many of the job losses had been achieved voluntarily.
Unions are threatening to take industrial action over pay-off terms.
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.
Mr Shopland said: "It is clearly a very positive and welcome development in what is a very difficult process.
"We've been able to mitigate the number of job losses to just over 600 and now it looks, for at least 60% of those, it's going to be achieved by voluntary means."
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 its refinery and drying unit.
China clay, or kaolin, has a variety of uses, but is mainly employed to whiten and give a glossy coating to paper.