Any ore, rock, or substance (other than oil, gas, or uranium) that is taken from below the surface or from the surface of the earth for the purpose of milling, concentration, refinement, smelting, manufacturing, or other use, or for stockpiling for future use. Calcium (Ca), phosphorus (P), magnesium (Mg), potassium (K), and sulfur (S) are normally expressed as a percentage of each in the feed. [Source: USDA National Plant Materials Manual]

« Back to Glossary Index