mineral matter

n

in coal, historically considered to be the non-organic fraction composed of physically discrete particles of minerals, such as clays, quartz, pyrite, etc., and all elements other than carbon, hydrogen, oxygen, nitrogen and sulfur in the organic fraction.

DISCUSSION — The mineral matter content is employed in the classification of coals according to rank (Classification D388). Since it is impractical to directly determine the proportion of mineral matter (for purposes other than scientific study of coals), it is customarily estimated from the ash residue following high-temperature combustion. A commonly used estimating technique is that attributed to S. W. Parr (Classification D388):

Mineral Matter = 1.08 Ash % + 0.55 Sulfur %

In higher-rank coals, the non-organic fraction is composed mainly of minerals such as those named above. In lower-rank coals it is made up of both minerals and non-mineral inorganics (sometimes collectively called inorganic matter) such as alkali and alkaline-earth cations bound to carboxyl and hydroxyl functional groups, hydrogen-bonded alkali metals, and other atomically distributed species. In combustion of both higher- and lower-rank coals, much of the inorganic matter reports to the ash residue while many of the decomposition products of some species such as hydrates, carbonates, and sulfates are lost to the gaseous phase. Note that the terms mineral matter and inorganic matter are often used interchangeably, although this is technically incorrect since the latter is a more-encompassing expression which includes the mineral matter.