Rocks and Rock Minerals: A Manual of the Elements of Petrology Without the Use of the Microscope, for the Geologist, Engineer, Miner, Architect, Etc., and for Instruction in Colleges and Schools

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J. Wiley & sons, 1908 - 414 pagina's
 

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Pagina 30 - SCALE OF HARDNESS 1. Talc 6. Feldspar 2. Gypsum 7. Quartz 3. Calcite 8. Topaz 4. Fluorite 9. Corundum 5. Apatite 10. Diamond...
Pagina 386 - ... stratified form are known as limestones, chalk, etc. It is distinguished from them by its crystallization, coarser grain, compactness, and purer colors. Pages 386-387 : The great deposits of marble, from which the material used for structural purposes is taken, are the result of original metamorphism, and it is thus found In regions of metamorphic rocks associated with gneisses, schists, etc., in the form of interbedded masses, layers, or lenses. These vary in size within wide bounds, from a...
Pagina 30 - ... are useful for testing the hardness of common minerals and of the rocks made up of them. A common brass pin point is a little over 3 and can scratch calcite; the fingernail is a little over 2 and can scratch gypsum. SPECIFIC GRAVITY. The specific gravity of a substance is its density compared with water, or the number of times heavier a given volume of the substance is than an equal volume of water. It is obtained by weighing a piece of the mineral or rock in air and then in water; the difference...
Pagina 141 - ... or shot, volcanic ashes; while the finest is volcanic dust. The divisional points may be supposed to lie midway between these sizes. The coarser material, the bombs, lapilli, and much of the ash, may fall around and near the vent and produce beds of breccia; the lighter ashes and dust, supported and carried by air currents, tend to fall after these and at greater and greater distances from the vent; their compacted material is known as tuff. Bailey (1926, p. 108) made the apt statement that definitions...
Pagina 237 - ... sills of dolerite occur in the Lake Superior region and in the great lava flows of the western United States. Dolerites are also common rocks in dikes and sills in Great Britain, in northern Scotland, and in Ireland. Dolerites are prevalent, in fact, in all parts of the world. Relation to other rocks. From what has been said it is easy to see that the dolerites are a class of rocks based largely on practical exigency. They form a transitional group, based on grain size, between gabbros and aphanitic...
Pagina 278 - Description. Fine gravel. Coarse sand. Medium sand. Fine sand. Very fine sand. Silt. Clay.
Pagina 81 - ... test will often be found convenient, since it can be applied to minerals which are not decomposed by sulphuric acid. If the finely powdered mineral is mixed with from 4 to 6 parts of sodium metaphosphate, transferred to a bulb tube (which should not be more than one quarter full), and heated very hot, hydrofluoric acid will be given off, which etches the glass, and deposits a ring of silica exactly as described in No. 2. This test is excellent for silicates when the proportion of fluorine is...
Pagina 89 - Fe3O4 =Fe"OFe'"2O3; the metallic iron content is 72.4 per cent. It is difficultly fusible before the blowpipe and in the oxidizing flame becomes nonmagnetic. It is slowly soluble in hydrochloric acid. Occurrence. Magnetite is one of the most widely distributed of all minerals. It occurs in igneous rocks of all kinds, generally in small grains but in some places aggregated into considerable masses. It occurs also in rocks produced by contact metamorphism and in the crystalline schists, sometimes in...
Pagina 23 - ... shapes in which each mineral is most likely to occur are described under the heading of that mineral in the descriptive part of this book. COLOR. The color of minerals, if used with caution, is a useful property for helping to distinguish them. Color may depend on chemical composition, when it can be said to be inherent, or it may be due to some foreign substance distributed through the minerals and acting as a pigment and can be termed exotic. Because the color of many minerals is exotic, caution...
Pagina 384 - CaCOj, and which in their ordinary stratified form are known as limestone, chalk, etc. It is distinguished from them by its crystallization, coarser grain, compactness, and purer colors. Marbles as thus defined have possessed attractions as ornamental stones for thousands of years past, and are now very extensively employed. From their crystalline character they take a high polish and lend themselves readily to these uses. It is well known that in trade usage, the term "marble...

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