1. Using Density for Mineral Separations
4th grade science experiment
Jack Groppo,
University of Kentucky,
Center for Applied Energy Research
2540 Research Park Dr., Lexington, KY 40511

2. Overview Experiment Objectives Materials Procedure
General Observations and Helpful Hints

3. Experiment Objective
To demonstrate how differences in mineral densities can be used to separate mineral mixtures into useful products.

4. Materials Needed 100 ml clear beaker per student/group
1 teaspoon CsCl salt for each student/group
50 mls water
2 Teaspoons per student/group
1 teaspoon crushed coal per student/group
1 teaspoon Crushed rock per student/group

5. Procedure
1. Place 50 ml of water into beaker and write down volume on a piece of paper.
2. Add 1 tsp CsCl salt into beaker and mix until dissolved.
3. Write down the difference in volume when salt is dissolved.
4. Add 1 tsp each of crushed coal and crushed rock.
5. Observe that coal floats and rock sinks in the solution.

6. General Observations and Helpful Hints
The volume increase when the CsCl salt is dissolved is a visual demonstration of molar volume. Even though you cannot see the salt, it is still present and it takes up space (volume).
The density of the CsCl solution is approximately 1.5 g/cm3. Since the density of coal is 1.4 g/cm3, the coal particles float. The density of rock is 2.4 g/cm3 and that is why the rock sinks.
Use white rocks such as limestone or quartz to dramatically emphasize the separation that occurs with the black-colored coal.

7. Resources for Materials
State Geological Surveys
Ward's Scientific (
Fisher Scientific (
Local rock and mineral trade shows