A Mineralogical Lexicon of Franklin, Hampshire, and Hampden Counties, Massachusetts

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U.S. Government Printing Office, 1895 - Mineralogy - 180 pages
 

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Page 17 - Its color is gray, sometimes with a faint reddish tinge, unless when acted on by the weather, when its color is yellowish. It is in indistinct prisms with oblique seams like zoisite, and in radiated or fascicled masses, which are composed of slender prisms. Luster somewhat shining or pearly. It is nearly as hard as quartz, and sometimes makes a slight impression upon rock crystal. Before the blowpipe it blackens, and a small portion melts, when the heat is very great, into a black slag, which is...
Page 7 - SIR: I have the honor to transmit herewith, for publication as a bulletin of the United States...
Page 111 - Shepard's had made the former a columbate of lime. This identity, strenuously resisted by Prof. Shepard, although on grounds which show a very superficial knowledge of the whole subject, has been completely proved by subsequent analyses, particularly by that of AA Hayes, in Silliman's Journal, vol. xxxii. p. 341, and its station as a columbate of lime, according to one of Shepard's analyses, confirmed. Dana's Mineralogy, one of the arrangements of which is crystallographical, although in the last...
Page 82 - ... ranging from a fraction of an inch to more than a foot in diameter, are now standing at every possible angle (Fig.
Page 58 - COPPEE. 1823. Native copper. Whately. In geest on the limit between the primitive and alluvial soil, and about 5 miles from the secondary greenstone of the coal formation. The piece weighs 17 ounces, exhibits imperfect rndiments of octahedral crystals on the surface, and is incrusted by green carbonate of copper.
Page 13 - ... broad interval from the other triclinic feldspars. The position of these crystals is interesting from a paragenetic point of view. The cavities are tapestried on all sides by the diabantite and the albite crystals rest upon it, often very loosely, and while forming they projected freely into the interior, as is shown by their glassy clearness and perfection of form and polish. The last of the diabantite seems sometimes to fill the cavities into which the albites project, but this could not be...
Page 73 - ... paragenesis of the mineral is thus quite definitely fixed. It was the first product of the decomposition of the diabase and its formation ceased not very long after calcite and prehnite began to be deposited in the cavities and fissures. As the formation of the latter minerals was attended by quite energetic decomposition of the trap, the formation of the diabantite occurring still earlier may well have been promoted by the increased chemical activity of the waters during the cooling of the trap...
Page 126 - ... at right angles to the long axis, and are soon twinned so as to allow a third crystal to wedge in between them and grow by the development of the same face. All three grow thus predominantly in the same direction and expose and add to only the single crystalline face, and the crystal expands in growing like the top of a growing tree. The common vertical axis of the three crystals is bent thus into a circle. When examined under the polarizing microscope, the central crystal, though showing a strong...
Page 73 - Ou the other hand, where over the botryoidal layer of diabantite there appear quartz, datolite, natrolite, sphalerite, or other sulphurets, they are entirely free from this impregnation. In the broad mineral-bearing fissures the diabautite often impregnates layers of scaly or fibrous prehnite 1 to 5 mm. thick over considerable surfaces so that a black or blackish-green mass results, often abundantly slickensided, which so resembles a very fine. grained scaly or fibrous schist that I supposed it to...
Page 70 - O, and the face f unusually large and shieldshaped. Similar tabular forms have been recently described from the spheres of chalcedony from Theiss in Tyrol.* ENCLOSURES IN DATOLITE. Calcite. — When the datolite is thrown in acid much calcite is dissolved and a vesicular mass left ; and similar pieces are found in the vein itself, showing that the same operation has been performed by natural agencies. Selenite? Barite ? — In the thick veins the minerals are often abundantly gashed by the removal...

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