Changes

==Sample preparation==

==Sample preparation==

Once samples have been selected, impregnation and thin sectioning procedures are critical to successful petrographic analysis. Samples are impregnated with low viscosity epoxy introduced while the samples are under a vacuum. After vacuum impregnation, some laboratories apply pressure via an inert gas to force the epoxy into small pores. The epoxy is stained, usually blue, to facilitate observation of porosity once thin sections have been completed. Epoxy can also be “stained” with fluorescent dye, either during impregnation or after thin sections are completed, to enhance observation of relatively small pores when thin sections are viewed under incident fluorescent light.<ref name=pt05r138>Ruzyla, K., Jezek, D. I., 1987, Staining method for recognition of pore space in thin and polished sections: Journal of Sedimentary Petrology, v. 57, p. 777–778, DOI: 10.1306/212F8C38-2B24-11D7-8648000102C1865D.</ref> Thin sections must be carefully ground to final thickness (usually 30 μm) to avoid fracturing and plucking.

Once samples have been selected, impregnation and thin sectioning procedures are critical to successful petrographic analysis. Samples are impregnated with low-viscosity epoxy introduced while the samples are under a vacuum. After vacuum impregnation, some laboratories apply pressure via an inert gas to force the epoxy into small pores. The epoxy is stained, usually blue, to facilitate observation of porosity once thin sections have been completed. Epoxy can also be “stained” with fluorescent dye, either during impregnation or after thin sections are completed, to enhance observation of relatively small pores when thin sections are viewed under incident fluorescent light.<ref name=pt05r138>Ruzyla, K., Jezek, D. I., 1987, Staining method for recognition of pore space in thin and polished sections: Journal of Sedimentary Petrology, v. 57, p. 777–778, DOI: 10.1306/212F8C38-2B24-11D7-8648000102C1865D.</ref> Thin sections must be carefully ground to final thickness (usually 30 μm) to avoid fracturing and plucking.

At this stage, samples can be stained for specific minerals if warranted by rock composition and objectives of the petrographic analysis. Common stains are available for calcite, dolomite, Fe²⁺ carbonate, K-feldspar, and plagioclase. Thin sections are then either covered or left uncovered. The conventional practice of gluing cover slips onto thin sections with either Canada balsam or epoxy is decreasing in popularity because many analyses must be performed on uncovered thin sections. Thin sections that are not polished can be “covered” with colorless fingernail polish. If thin sections are to be analyzed by cathodoluminescence or microprobe techniques, they must be polished to yield suitable results.

At this stage, samples can be stained for specific minerals if warranted by rock composition and objectives of the petrographic analysis. Common stains are available for [[calcite]], [[dolomite]], [[Fe²⁺ carbonate]], [[K-feldspar]], and [[plagioclase]]. Thin sections are then either covered or left uncovered. The conventional practice of gluing cover slips onto thin sections with either Canada balsam or epoxy is decreasing in popularity because many analyses must be performed on uncovered thin sections. Thin sections that are not polished can be “covered” with colorless fingernail polish. If thin sections are to be analyzed by [www.geology.wisc.edu/~johnf/g777/CL/Gotze-CL-2002.pdf cathodoluminescence] or [[Wikipedia:Electron microprobe|microprobe]] techniques, they must be polished to yield suitable results.

==Petrographic techniques==

==Petrographic techniques==