Light microscopy of silicosis of lung. Nodules of collagen contain silica particles. Additional carbon pigmentation results in black peripheral staining. Silicosis is a type of pneumoconiosis caused by exposure to silica dusts. Symptoms include breathlessness and a chronic cough. There is no cure for silicosis, treatment is aimed at reducing the symptoms. Silicosis is most prevalent in people working in the mining and quarrying industries.