The Unimin Corporation has announced that it will temporarily lay off nearly 70 workers in two of its four plants in Mitchell County. Unimin mines feldspar in Mitchell County used in making computer chips and for other high-tech industries and says the reason for the layoff is a downturn in their customers’ business.  They blame the cutbacks on a downturn in orders from solar panel manufacturers. Unimin mangers say they don’t know when the workers could return. They plan two temporary layoffs, first with 37 workers at one plant, and about 30 at the second plant.