Oil Flotation

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Students can see how sulfides can float to the surface in a simple experiment using ground pyrites and sandstone mixture.  Be sure to connect the exploration to the Carrie Everson Story. Why would a method other than panning and sluicing be necessary to capture the smallest of gold flakes?

To replicate the oil flotation process use a mixture of ground sandstone or sand and powdered galena or pyrite.  Using a rock containing either of these would be more realistic.

1) Grind the rock into a powder and sieve it so that only the smallest pieces are used.

2)  Add the powder to a container and fill the container 1/3 full with water.  

3) Pour a layer of vegetable oil on the surface of the water. Not much is needed--only a few millimeters thick will do.

4) Agitate the mixture with a spoon and add air (if desired) by blowing into the mixture with a straw.  

5) Observe the surface of the oil for evidence of floating minerals.

6) Experiment with other materials, acids or oils to determine how the flotation process might have helped remove certain minerals.

We want students to make good observations and inferences about what they find. Ideally a field note form would be placed in the STEM Notebook to help students record their findings.  This form should include name, date, team members, a brief statement of the analysis under investigation, and all pertinent data relating to the work.  Data should be labeled appropriately.  Students should take opportunity to make reflective statements about the processes involved in oil separation.

Why do you suppose early mining engineers were not interested when they were shown the flotation process?

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