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U. S. Geological Survey Open-File Report 01-041

A Laboratory Manual for X-Ray Powder Diffraction

SMEAR SLIDE SAMPLE MOUNTS FOR X-RAY POWDER DIFFRACTION

Samples may be ground and smeared on the surface of a glass slide as a rapid means of preparing samples for X-ray powder diffraction. This mounting method seldom produces acceptable random orientation of the crystallites, resulting in diffraction maxima with relative intensities that are not accurately reproduced. Although not useful for semi-quantitative analysis, this method is useful for rapidly determining bulk mineralogy, especially if the operator knows which mineral phases are likely present.

PREPARATION OF SMEAR-SLIDE MOUNTS 
Materials Required:
  • weighing paper (4"x4")
  • mortar and pestle
  • spatula
  • glass rod
  • marker pen
  • glass slide cut to fit the diffractometers's
    sample holder
  • acetone in a squeeze bottle
  • lab tissues
  • diamond or carbide scribe to cut slides
 Materials required for smear-slide mounts.
Grind the dried sample thoroughly with the mortar and pestle. The particles should be much finer than .062 mm to avoid fractionation of the minerals. The finer the powder the greater the opportunity for obtaining an adequate number of particles with random orientation and the less likely that surface roughness will reduce low-angle intensities. Grind the dried sample throughly with the mortar and pestle.
Use the spatula to loosen any sample that has stuck to the mortar and to homogenize the powder.  Use the spatula to loosen any sample that has stuck to the mortar and to homogenize the powder.
Place a small amount of sample in the center of the slide and add an amount of acetone sufficient to wet the sample (2-3 drops). Distilled water may be used, but the sample dries quicker with acetone. Add 2 to 3 drops of acetone sufficient to wet the sample on the glass slide.
Spread the sample into a thin layer with the glass rod. Gently blow on the slide to rapidly evaporate the acetone. Use the spatula or a finger to remove any excess sample sticking to the edges of the slide. Use a lab tissue to remove any sample stuck to the back of the slide. Spread the sample into a thin layer with the glass rod.
Label the slide with a marker pen. Brush the sample from the mortar onto the weighing paper and transfer the remaining sample back into a sample vial. Brush the sample from the mortar onto the weighing paper and transfer the remaining sample back into a sample vial.

 

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