A popular guide to minerals : with chapters on the Bement Collection of minerals in the American Museum of Natural History, and the development of mineralogy . ZINCITE Franklin Furnace, N. J. BOLEITE Boleo, Lower Cal. Bement Collection, American iNIuseum of Natural History DEFINITION OF TERMS /3 along- two directions, the optic axes, and these crystals are calledbiaxial. Now practically all optical examinations of natural crystals(usually in thin sections) are made by polarized light and suchpolarized light may be parallel or convergent and it is usually pro-duced by the passage of ordinary li
A popular guide to minerals : with chapters on the Bement Collection of minerals in the American Museum of Natural History, and the development of mineralogy . ZINCITE Franklin Furnace, N. J. BOLEITE Boleo, Lower Cal. Bement Collection, American iNIuseum of Natural History DEFINITION OF TERMS /3 along- two directions, the optic axes, and these crystals are calledbiaxial. Now practically all optical examinations of natural crystals(usually in thin sections) are made by polarized light and suchpolarized light may be parallel or convergent and it is usually pro-duced by the passage of ordinary light through a polarizer by whichthe light is polarized. Above such a polarizer in the tube of amicroscope is placed another polarizer which however in this posi-tion is called an analyzer: and between the polarizer and the an-alyzer the thin section under examination is placed (Fig. 271)upon a stage. The polarizer and analyzer consist of nicol prismswhich are made of cleavage rhombohedrons of calcite, three timesas long as broad; these are cut as in the oblique plane in Fig. 272,and the halves cemented together with Canada balsam^ and, theends are groun
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectmineral, bookyear1912
