Between 70 and 80 jobs are to be cut at Cornwall's biggest private employer.
China clay firm Imerys said global trading conditions are forcing it to restructure.
Increase in the cost of energy, chemicals and freight, as well as current exchange rates, have put pressure on finances, managers say.
A 30-day consultation period is to take place with trade unions to discuss the changes. Any redundancies will happen in spring next year.
Managers say they are developing a number of strategies which include a review of improving the company's efficiency.
The jobs are most likely to be lost in the division which sells to the paper industry.
Restructuring will also take place in departments such as operations support, mining and port operations, but the firm admitted that staff in all areas would be affected.
The firm said it was disappointed about the news but that it was essential that it responded to the increase in costs which it could not control.
Ivor Bowditch from Imerys said: "We've seen huge increases in the cost of the materials that we use to process china clay. Energy is up 50% and chemicals in some cases are up between 80 and 100%.
"It's a hugely difficult decision to make, particularly at this time of year.
"We hope that as many possible of the redundancies will come voluntarily, but it will not be until the early new year that we will see where the jobs will come from."