By polarized light microscopy can be seen the etiology for most pneumoconioses (even those in coal miners)--silica crystals. Here are seen bright white crystals of varying sizes. The silica induces a fibrogenic response by macrophages to produce the nodular foci of collagen deposition.

Increasing use of engineered stone products, such as man-made quartz countertops, represents a hazard for inhaled silica when the stone is cut and/or polished, without appropriate respiratory precautions. Engineered stone may have a higher content of silica than natural stone. Once the finished product is installed, there is no silica hazard.