McAlpine's Penrhyn quarry in Bethesda

But McAlpine Slate and the T&G union said the jobs at Bethesda would go through natural wastage as the quarry diversified.

Workers unwilling to retrain on the new machinery will be offered early retirement.

It is hoped the investment will result in more jobs being created at its other plant at Blaenau Ffestiniog.

McAlpine Slate said the job losses follow new working practices when the new machinery comes into operation in April 2006.

'Goodwill gesture'

It became clear during negotiations with the union that fewer people would be required to operate the new plant.

Chris Law , the manager of McAlpine Slate in Bethesda, said the new machinery was needed because the company are diversifying into other slate products.

T&G union officer Paddy McNaught, said the future looked bright.

The union has accepted a "goodwill gesture" by the company of a generous early retirement package for workers who did not want to retrain for the new machinery.

"The new investment could mean more new jobs in their other plant at Blaenau Ffestiniog," Mr McNaught added.