Dust arising from the crushing or other dry working of sand, sandstone, trap, granite, and other igneous rocks is included in this class. Siliceous dusts are not soluble in body fluids, and when introduced into the respiratory tract in the form of particles of certain sizes and in sufficiently high concentration, they produce nodular growths that often result in a form of pneumonoconiosis that has been known as silicosis or "stone cutters" consumption.