BUREAU OF GEOLOGY


fiber A plant fragment in a peat or soil which is greater than .15 mm
in any dimension.

fuel grade peat (U.S. Department of Energy definition) Peat with less
than 25 percent ash content, heat value greater than 8,000 BTU/lb (dry
weight) and which is found in areas with more than 80 acres per square
mile of peat, at least 4 feet thick. Generally, hemic peats have the great-
est heat value.

fibric peat (U.S. Department of Agriculture classification) Peat con-
taining more than 66.66 percent plant fibers (see also hemic and sapric).

fixed carbon In coal, coke and bituminous materials, the remaining
solid, combustible matter after removal of moisture, ash and volatile
matter, expressed as a weight percentage, following the procedures
specified by the American Society of Testing and Materials.

fluidized bed boiler A boiler design in which the fuel is agitated or
"boiled" by the introduction of air from beneath the fuel bed.

gasification In fuel technology, the conversion of a solid or liquid
hydrocarbon to a fuel gas.

geology The study of the planet Earth. It is concerned with the origin
of the planet, the material and morphology of the Earth, and its history
and the processes that acted (and act) upon it to affect its historic and
present forms.

graphite A hexagonal mineral, representing a naturally occurring
crystalline form of carbon dimorphous with diamond. It is opaque, lus-
trous, very soft, greasy to the touch and iron-black to steel-gray in color;
it occurs as crystals or as flakes, scales, laminae or grains, in veins or
bedded masses or as disseminations in metamorphic rocks. Graphite
conducts electricity and heat, and is used in lead pencils, paints, and
crucibles, as a lubricant as electrodes, and as a moderator in nuclear
reactors. Syn: plumbago; black lead.

grate fired boiler Boiler design in which the fuel load is supported by a
framework of metal bars.

gypsum widely distributed mineral consisting of hydrous calcium sul-
fate: CaSO4.2H20. It is the commonest sulfate mineral and is frequently
associated with halite and anhydrite in evaporites or forming thick,
extensive beds interstratified with limestone, shales and clays. Gypsum
is very soft (hardness of 2 on Mohs' scale) and is white or colorless when
pure, but can be tinted grayish, reddish, yellowish, bluish or brownish. It
occurs massive (alabaster), fibrous (satin spar) or in monoclinic crystals


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