Minerals in rock sections; the practical methods of identifying minerals in rock sections with the microscope, especially arranged for students in technical and scientific schools . ay be used when asection is required parallel to the face of the crystal cemented tothe holder. In these machines the cutting is done with rotating saws ofsheet-tin, usually charged with either diamond dust or emery. In the case of a very small crystal a section, parallel to any de-sired face, can be obtained by cementing this face to a suitableframe or holder and grinding down by hand on a glass plate withemery, t
Minerals in rock sections; the practical methods of identifying minerals in rock sections with the microscope, especially arranged for students in technical and scientific schools . ay be used when asection is required parallel to the face of the crystal cemented tothe holder. In these machines the cutting is done with rotating saws ofsheet-tin, usually charged with either diamond dust or emery. In the case of a very small crystal a section, parallel to any de-sired face, can be obtained by cementing this face to a suitableframe or holder and grinding down by hand on a glass plate withemery, the final polishing being given with rouge. When the sec-tion required is not parallel to a crystallographic face or cleavageit must be verified geometrically with reference to other faces. Ifthe crystals are soluble in water, some other liquid, as a brom-naphthalin or benzine must be used in grinding ; and very fragilecrystals are rubbed down on a ground glass plate without emeryor rouge, simply using bromnaphthalin or some other appropriateliquid. When sections of a crystal are desired with strictly parallel faces,the form of grinding apparatus shown in Fig. ]] can be This apparatus consists of a cylinder, held within a suitableframe supported on three set-screw^s «,, a.^ and a^^ of hard lower surface of the frame and consequently the bottom of thecylinder can be adjusted by the wedge k and the set-screws so thatit is exactly parallel to the grinding surface of the glass crystal to be ground down, /, is cemented to the bottom of 114 METIWDS OF PRFPARING SECTIONS. the cylinder, and the whole apparatus rubbed over the grindingsurface of the plate. The pressure of the hand on the upper partof the cylinder regulates the pressure of the crystal on the grind-ing surface. In this way a surface is obtained which is exactlyparallel to the surface cemented to the cylinder. Sections of definite thickness can also be obtained by using thisapparatus ; for the ad
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Keywords: ., bookcentury1900, bookdecade1900, bookpublishernewyorkdvannostran
