n. Total ash content minus the silica content.
Mineral ash or silica-free ash is a measure of the quantity of trace minerals present in the parent material. Silica is generally the most prevalent material in ash. By immersing ash in acid, all but the silica can be removed and thus the mineral ash or silica-free ash content can be derived. Some research has indicated a link between silica content and reduced capacity for combustion; however, this is not the case regarding ignitability. The mineral ash content of vegetation may influence soil chemistry after fires and palatability of plants; it indicates the presence of trace elements (such as phosphorus, iron, magnesium, and manganese).