Mineral Reserves

• Cardboard boxes (similar to those that a ream of copy paper comes in; collect enough to establish groups of 2–3 per box)
• Several boxes of plaster cloth sheets, such as E-Z Form Plaster Cloth Wrap (these can usually be found at craft and hobby stores)
• 8 bags of clean, dry brown sand, also known as “play sand” 400# (contact your local aggregate supplier or your local home improvement store for assistance)
• 1 box of plastic sipping straws

Mineral reserves—including sand, gravel, limestone, granite and other aggregate and construction materials—are valuable resources that contribute to our everyday lives. Common uses include road and construction materials such as asphalt and concrete roads, sidewalks, school buildings, hospitals and homes.

These important resources are underground, and technicians and scientists utilize various tools to determine the quantity and quality of these materials.  This information is crucial to predict the value of a mineral deposit to determine whether mining the deposit could be profitable.  A knowledge of mineral reserves is also important to determine whether future demand can be met for uses of the mineral in society.  Questions about mineral reserves are being asked in relation to the future of green energy and electric vehicles that require large amounts of specific minerals.

Student Challenge

Students work in small groups to determine the volume of mineral reserves.

Success Criteria

• Demonstrate the ability to compute the volume of aggregate (sand) above the bedrock.
• Create a method of organizing drill sites to determine the topography of the bedrock below the aggregate.
• Draw a diagram depicting the placement of drilling sites.
• Analyze data to determine the volume of the aggregate.
• Formulate the predicted volume based on their data and determine the actual volume.
• Compare predicted volume to actual volume and compute percent error.

1. After obtaining the items outlined in the Materials list, assemble the boxes students will use to determine the volume of aggregate (sand) above the bedrock.
2. Place plaster cloth sheets in your box to simulate a rolling, undulating surface. This represents the surface of solid bedrock. Use wadded paper or other materials to create an irregularly shaped contour. Use duct tape to close openings between plaster cloth and box sides; this will eliminate the loss of sand when calculating the volume of sand in the box. Be sure to vary the topography of the bedrock to make it challenging for your students.
3. Have students fill the boxes with sand and spread a level surface approximately 2”–3″ below the box top. Once that is completed, have groups trade boxes. 
4. Ask students to calculate the volume of aggregate (sand) in the box above the bedrock. Inform students that they cannot take the sand out to measure its true volume until the very end.
5. To calculate the volume, have groups “drill” five holes throughout their territory and measure the depth of each drill hole. Inform students that they may use straws or a ruler to drill, mark, and measure where they drill.  Have students create a diagram, like a map, and mark the locations of the drill holes. Ask students to consider why they are choosing these locations. Lead a class discussion about how groups will use their measurements to calculate a volume.
6. Have students “drill” into their chosen drill sites and record the measured depth at each location. Students should use the strategy they decided on in the previous step to calculate the volume of aggregate. Once students have “estimated” as closely as possible using their system of measuring volume, have them measure the actual volume using large beakers or measuring cups.
7. Ask students to use the following equation to calculate the accuracy of their results. 

Percent error = [your value – actual value] X 100 Actual value

8. Use the Guiding Questions to lead a class discussion about outcomes.

Figure 1. Box without the sand. Note the irregular bottom surface of the empty box.

Figure 2. Box with the sand added and five straws used to estimate the volume of sand in the box.

1. What were their sources of error?
2. What would they do differently to decrease the percent error?
3. Would a different “drill pattern” give more accurate results?
4. Would more “drill holes” have helped?
5. In the real world each “drill hole” costs money, so how many more could you afford?

Next Generation Science Standards

Science and engineering practice—Developing and using models, Using mathematics and computational thinking

Crosscutting Concepts—Systems and system models 

Disciplinary Core Ideas—Natural Resources 

©Minerals Education Coalition 2022