A specimen of an ore (opaque) mineral after it has been prepared for examination under a reflected-light microscope by light reflected from its polished surface. A sample of the mineral is mounted in a cold-setting epoxy resin, sawn to produce a flat surface, and then inverted, ground, and polished in a number of stages using diamond-impregnated fluids and a rotating lap fitted to a polishing machine. Conventional 0.03 mm thin sections are prepared in the same way to give ‘polished thin sections’, used in the identification of opaque minerals. Polished sections are also required in the electron-probe microanalyser to enable analyses of minerals to be carried out.
Subjects: Earth Sciences and Geography.