Nodules of spheroidal, lenticular, or irregular shape containing petrified
plant remains and in some cases animal remains. They vary in size from
about 1 to 40 cm or more; occasional specimens weigh more than 1 ton.
Infrequently, an entire seam in a restricted area consists largely of coal
balls. Coal balls consist mainly of calcareous, dolomitic, sideritic,
pyritic, or siliceous material surrounding or impregnating plant and
animal remains. They occur in brown coals (mainly sideritic balls) as well
as in coals of higher rank generally lying within a coal seam but
occasionally in the roof. Calcareous, dolomitic, and pyritic coal balls
are commonly found in seams having marine strata in the roof. The
distribution in seams is variable. They may occur in a broad zone running
through a coalbed or be distributed irregularly in nests.
Syn: torf dolomite
Dictionary of Mining, Mineral, and Related Terms