- Term used to designate extent to
which metamorphism has advanced. Compare with
grade. Rank is more commonly employed in designating stage
of metamorphism of coal.
Source: Leet, L. Don. 1982.
Physical Geology, 6th Edition. Englewood Cliffs, NJ: Prentice-Hall
- a. Describes the stage of carbonification attained by a given coal.
b. The place occupied by a coal in a classification. Specifications of the
American Society for Testing and Materials cover the classification of
coals according to their degree of metamorphism, or progressive
alteration, from lignite to anthracite. For a complete description of this
classification, consult ASTM Designation: D 388. ASTM
c. When applied to coal, denotes its age in geological formation, not
necessarily denoting quality. BCI
d. The position of a coal relative to other coals in the coalification
series from brown coal (low rank) to anthracite (high rank), indicating
its maturity in terms of its general chemical and physical properties.
e. Those differences in the pure coal material due to geological processes
designated as metamorphic, whereby the coal material changes from peat
through lignite and bituminous coal to anthracite or even to graphite.
f. All coallike fossil fuels form a continuous and progressive series,
ranging from lignite, through the various bituminous coals, to anthracite.
It is the position of a particular coal in this series that determines its
rank. Therefore, lignite is a low-rank coal while anthracite is a
high-rank coal. See also: coalification;
grade; Hilt's Law;
g. A term primarily devised to indicate the position of a fuel in the
series peat-anthracite, probably best measured by the percentage of carbon
(ashless, dry basis). Thus rank depends on the degree of metamorphism of
coal, and increase of rank is, in general, marked by the decrease of
volatiles and moisture. Tomkeieff
h. The term rank may also be applied to other series, such as the
sapropelic coal series or the bitumen series. CF:
Dictionary of Mining, Mineral, and Related Terms