In a recent article,3 we described three patients with anthracofibrosis that was attributed to mixed mineral dust exposure. None of the patients had a history of tuberculosis. They had experienced occupational exposure to silica, silica and aluminum, and silica and asphalt. Mineralogical analysis by transmission electron microscopy of BAL fluid, pulmonary, hilar, or bronchial samples found high levels of particle retention. Two patients had high percentages of free crystalline silica and mica, and the third patient had high percentages of free crystalline silica, kaolin, and other silicates. These findings suggested that mixed mineral dust was the cause of the anthracofibrosis.