Bulletin, Issue 25 |
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acid alloy analyses brittle brownish Burke County calcium carbon cent of thoria cerium chemical chromite color Colorado columbite commercial Company composition concentrates considerable Creek crystals electric electro-magnets feet feldspar fergusonite filament fracture gadolinite garnet Geological glower gneiss gold Magnetite granite gravels gummite hardness heated hydrous Idaho ilmenite incandescent lamps inch iron Jour Llano County locality magnetic separators Magnetite manganese mantle manufacture masses metal mica miles mill minerals containing mines Mitchell County monazite monazite sand niobate North Carolina obtained occurs pegmatitic pegmatitic dikes pegmatized percentage Placer deposits platinum pounds principally quartz rare earth rocks rutile scheelite schist silicate small amount South Dakota specific gravity steel Survey tantalate tantalite tantalum lamp tantalum minerals tested thoria thorianite thorium thorium nitrate titanium tungsten tungsten lamp U. S. Geol United uraninite uranium usually vanadate vanadium varies vitreous Welsbach Wilfley table wire Yancey County yellow yttria yttrium oxides zircon zirconia zirconium
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Page 70 - In these experiments there was observed for the first time a minute globule of molten tantalum, and this globule was of sufficient toughness to permit hammering and drawing into wire. Following out this observation, tantalum powder was melted in a vacuum, and then it was found that the highly heated metal parted with the gases it contained. In this manner I produced my first filaments of pure metallic tantalum, which were, however, very small. When these had been used in lamps with promise of good...
Page 27 - The mineral is usually readily recognized after a few samples have been examined. Its color, usually yellowish inclined to reddish, its hardness, 5 to 5.5, being readily scratched by feldspar (hardness 6) or quartz (hardness 7), and its high specific gravity, 4.64 to 5.3, are the chief macroscopic properties that will aid in distinguishing it.
Page 54 - The supply of monazite in the stream-gravels in favorable areas is often replenished by the wash from the hill-side soils during rains, especially where the hills have any considerable slope and the land is cultivated. Under such conditions the stream-gravels are often worked two or more times in a year.
Page 71 - ... by fusion and drawn into wire it has a specific gravity of 16.8. It is somewhat darker than platinum and has a hardness about equal to that of mild steel, but shows greater tensile strength than steel does. It is malleable, although the effect of hammering is relatively small, so that the operation must be rather long and severe to beat the metal into a sheet. It can be rolled as well as drawn into very fine wire. Its tensile strength as a wire is remarkably high and amounts to 95 kilograms per...
Page 93 - Rutile crystallizes in the tetragonal system commonly in prismatic crystals vertically striated or furrowed; often slender acicular. It is also compact, massive to coarse and fine granular. Twinning is frequent and of several kinds. Cleavage distinct; fracture subconchoidal to uneven. Brittle. Hardness 6 to 6.5. Specific gravity 4.18 to 4.25; also to 5.2 in a black variety containing 10 per cent FeO. Lustre, metallicadamantine. Color reddish-brown, passing into red ; sometimes yellowish, , bluish,...
Page 33 - Welsbach mantle consists of a cylindrical hood composed of a net-work of the rare earths, the top of which is drawn together and held by a loop of asbestos or platinum wire. When in use, this mantle is suspended over the flame of a burner constructed on the principle of the Bunsen burner, in which the heating instead of the illuminating power of the hydrocarbon of the gas is used by burning it with an excess of air. In this manner the mantle becomes incandescent and glows with a brilliant and uniform...
Page 72 - ... (25 Hefner candlepower 110 volts). This shape offers a number of noticeable advantages. In the first instance it is very stable and will stand strong shocks without damage to the lamp. A considerable number of such lamps sent across the sea to test their ability to withstand the hardships of transport came back unhurt, although they had been packed just like common glow lamps, and no special care in any respect had been taken in their handling. The lamp burns, of course, in any position, and...
Page 27 - ... as the yttrium and erbium oxides, zirconia, alumina, magnesia, lime, iron oxides, manganese oxide, and titanium oxide. Monazite is light-yellow, honey-yellow, reddish-, brownish-, or greenish-yellow in color, with a resinous to vitreous luster, and is translucent to subtransparent. It is brittle, with a conchoidal to uneven fracture, and is from 5 to 5.5 in hardness, and from 4.64 to 5.3 in specific gravity. It crystallizes in the monoclinic system, and some crystals have been observed that were...
Page 45 - ... enclosing rocks through part of its extent and cutting across them in other parts, or in irregular masses having no definite orientation with respect to the accompanying formations. All the rocks in this area are more or less weathered and decomposed and a clue to the nature of the rock formations themselves is often obtained by a study of the character of the gravels in the bottom lands and streams draining a particular region. Thus, a very light colored gravel with quartz debris indicates a...
Page 54 - The partial concentration of monazite in the top layer of soil is caused by the washing away of the clay and other light decomposition products of the rock. The supply of monazite in the stream gravels in favorable areas is often replenished by the wash from the hillside soils during rains.