Having obtained the figure, the stage of the petrographic polarizing microscope should be turned so that the trace of the optic axial plane occupies an oblique position. The converging apparatus should be removed and the section examined in parallel polarized light of the polarizing microscope by means of the low power objective. Testing with the […]

It is not necessary that a mineral section, which has been prepared specially to give an interference figure, should have the same thickness as an ordinary rock section. In fact, it is only in the case of minerals with a very high double refraction that such a thin section gives the best results. As a […]

In fitting up the petrographic polarizing light microscope, the instrument is first arranged as for use with parallel polarized light. The high power objective that is usually ¼ inch must be used. A system of converging lenses is fitted either beneath the stage or above the polarizer, and a lens called Bertrand Lens is placed […]

In considering the examination of transparent mineral plates, it has already been seen that there are three conditions of the microscope, all of which must be used in turn if we are to acquire a satisfactory amount of information in regard to the minerals in thin section. Even after this examination, it is not always […]