A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

U

Ultimate analysis       Precise determination, by chemical means, of the elements and compounds in coal.

Ultra basic       Igneous rocks containing less than 35% silica.

Umpire sample or assay       An assay made by a third party to provide a basis for settling disputes between buyers and sellers of ore.

Uncut value       The actual assay value of a core sample as opposed to a cut value which has been reduced by some arbitrary formula.

Undercut       To cut below or undermine the coal face by chipping away the coal by pick or mining machine. In some localities the terms "undermine" or "underhole" are used.

Underground mine       Also known as a "deep" mine. Usually located several hundred feet below the earth's surface, an underground mine's coal is removed mechanically and transferred by shuttle car or conveyor to the surface.

Underground station       An enlargement of an entry, drift, or level at a shaft at which cages stop to receive and discharge cars, personnel, and material. An underground station is any location where stationary electrical equipment is installed. This includes pump rooms, compressor rooms, hoist rooms, battery-charging rooms, etc.

Underwrite       A firm commitment made by a broker or other financial institution to purchase a block of shares at a specified price.

Unit train       A long train of between 60 and 150 or more hopper cars, carrying only coal between a single mine and destination.

Universal coal cutter       A type of coal cutting machine which is designed to make horizontal cuts in a coal face at any point between the bottom and top or to make shearing cuts at any point between the two ribs of the place. The cutter bar can be twisted to make cuts at any angle to the horizontal or vertical.

Unpatented claim       Usual lode, placer or millsite claim located under the mining laws.

Upcast shaft       A shaft through which air leaves the mine.

Upper lead       Pay gravel of pay streak in a gravel deposit that lies in strata well above bedrock.

Uraninite       A uranium mineral with a high uranium oxide content. Frequently found in pegmatite dykes.

Uranium       A radioactive, silvery-white, metallic element.