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Title Description
 Ultramarine Yellow   

A lemon-yellow pigment consisting of barium chromate.  
 Underground Glory-hole Method   

A method used in large deposits with a very strong roof. In this method, a deposit is divided by levels and on every level chutes are raised to the next one. Mining starts from the mouth of the chutes in such a way as to develop a funnel-shaped excavation (mill, glory) with slopes so steep that the broken ore falls into the chutes and thus to the cars on the lower level. A sufficiently strong pillar is left for protection at the higher level. Syn: underground milling 
 Undation Theory   

A theory proposed by Van Bemmelen (1933) that explains the structural and tectonic features of the Earth’s crust by vertical upward and downward movements caused by waves that are generated by deep-seated magma. 
 Ultimate Analysis   

A. The determination of the elements contained in a compound, as distinguished from proximate analysis, which is the determination of the compounds contained in a mixture. Standard, 2
B. In the case of coal and coke, the determination of carbon and hydrogen in the material, as found in the gaseous products of its complete combustion, the determinations of sulfur, nitrogen, and ash in the material as a whole, and the calculation of oxygen by difference. 
 Unconformity   

Buried erosion surface separating two rock masses, older exposed to erosion for long interval of time before deposition of younger. If older rocks were deformed and not horizontal at time of subsequent deposition, surface of separation is angular unconformity. If older rocks remained essentially horizontal during erosion, surface separating them from younger rocks is called disconformity. Unconformity that develops between massive igneous or metamorphic rocks exposed to erosion and then covered by sedimentary rocks is called nonconformity. 
 Uniaxial Stone   

One that has crystallized in the tetragonal, trigonal, or hexagonal crystal system and, therefore, has only one direction or axis of single refraction. CF: biaxial stone
Source: Dictionary of Mining, Mineral, and Related Terms










 
 Ultramafic   

Said of an igneous rock composed chiefly of mafic minerals, e.g., monomineralic rocks composed of hypersthene, augite, or olivine. 
 Unconsolidated Surface Deposits   

Surface deposits such as moss, peat, sand, gravel, silt, or mud.  
 Ultimate Tensile Stress   

The load at which a test piece breaks, divided by its original area.  
 Undermine   

To excavate the earth beneath, esp. for the purpose of causing to fall; form a mine under 
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