eTraining Introduction

Specimen Preparation

Leica Ultracut UCT

Histology

JEOL JSM-6400 SEM

Hitachi S-4700 FE-SEM

Hitachi FB-2000A FIB

Microanalysis

Veeco Dim 3000 AFM

Fluorescence Microscopes

Support

Rocks and Minerals

See Making Acrylic Mounts in Mount Fabrication Procedure under Specimen Preparation.

Polishing Rocks and Minerals

Content additions courtesy of Dr. Rod Johnson.

Generally, rock and mineral specimens are polished flat. Examples include thin sections and polished mounts. Thin sections are most commonly studied with transmitted light using the petrographic microscope. Thin sections are ground to a thickness of 30 μm to permit the transmittal of visible light through the rock and/or mineral. The effort to produce a thin section is unnecessary for the SEM. Remember that polished specimens are ideal for X-ray microanalysis, as they fit the criteria for quantitative X-ray analysis using matrix correction programs like ZAF. This discussion of polished specimens does not imply that irregularly shaped geologic materials are not suitable for SEM analysis.

There are some polishing issues that are peculiar to rocks and minerals. Some rocks like quartzite are hard, while limestone is relatively soft. Each rock would require a different polishing procedure. The production of a good polished surface in rock specimens is further complicated because rocks are composed of a collection of minerals of varying hardness. This variation can produce an uneven surface during grinding and polishing; an undesirable outcome when you plan to conduct microanalysis. Careful selection of abrasive grade and polishing times is critical to reduce this phenomenon. Soft minerals may be plucked or removed from the rock during grinding and polishing. Vacuum impregnation is often required to reduce plucking in rocks with minerals of varying hardness or when pore space is present.

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