This review details a selection of occupational lung diseases, particularly fibrosis (scarring) and tumours that can arise following exposure to mineral dusts. Also described are the sequential repair processes of the lung including oedema, inflammation, epithelial changes and finally scarring. The features by which a dust can be considered bioreactive including shape, size, surface area, durability and surface chemistry is discussed together with the importance of the mass deposited in the lung and particle clearance, particularly through lymphatic drainage. Emphasis is given to the importance of surface chemistry in that crystalline minerals, especially silicas, are often highly bioreactive whereas amorphous silicas or crystalline forms that have aged in the laboratory have lesser activity. Nevertheless, all forms of crystalline silica are particularly hazardous with the long-term ability to produce irreversible disease (fibrosis) when administered to experimental animals.