Cathodoluminescence microscopy (CLM) is uniquely applicable to the study of industrial minerals. Most of the industrial minerals have a strong positive response to the electron microbeam and therefore they emit a variety of characteristic colors of catholuminescence (CL). CLM provides rapid identifications, effective examination of textural intergrowths, and an elegant means of recording those textures as CL micrographs. Cathodoluminescence is produced as a result of the emission of visible radiation when an electron shifts from an outer orbit to an orbit of lower energy level. Therefore, the color of CL is a function of the elements, especially minor transition and lanthanide elements, present in a mineral rather than the other properties of the mineral. Although a given mineral can exhibit more than one CL color due to the presence of various trace elements, certain colors tend to be most characteristic for each mineral. In contrast to the CL activator elements, other minor elements may act as CL quenchers. Industrial minerals that typically exhibit characteristic CL include: potash feldspar, plagioclase, calcite, dolomite, fluorite, wollastonite, talc, tremolite, sillimanite, kyanite, andalusite, anthophyllite, apatite, collophane, zircon, corundum, barite, diopside, garnet, and quartz. Other minerals that exhibit distinctive CL include: scheelite, smithsonite, cerrusite, anglesite, baddeleyite, cassiterite, sphalerite, pitchblende, uranopilite, schroeckingerite, diamond, and emerald. Some of the minerals commonly grouped with the industrial minerals that typically do not exhibit CL include: ilmenite, graphite, chromite, olivine, and mica. CLM should be a routine tool in the study of most industrial minerals.
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