Materials Included In Kit

Additional Materials Required

Prelab Preparation

Prepare two large samples of ore according to the following chart. Place the samples in large plastic bins and label the samples “A” and “B,” respectively.

Safety Precautions

The materials in this lab are considered nonhazardous. Use caution to avoid spilling the samples on the floor as spills may cause someone to slip and fall. Remind students to wash their hands thoroughly with soap and water before leaving the laboratory. Please review current Safety Data Sheets for additional safety, handling and disposal information.

Disposal

Please consult your current Flinn Scientific Catalog/Reference Manual for general guidelines and specific procedures, and review all federal, state and local regulations that may apply, before proceeding. All materials included in this kit are reusable and may be stored for future use. The aluminum and copper pieces and gravel may be disposed of according to Flinn Suggested Disposal Method #26a.

Lab Hints

• Enough materials are provided in this kit for 30 students working in pairs or for 15 groups of students. This activity can reasonably be completed in one 50-minute class period. The prelaboratory assignment may be completed before coming to lab, and the data compilation and calculations may be completed the day after the lab.
• When the activity is performed as written, three to five balances should be sufficient to prevent long wait times for measurements. If enough balances are available for each group, students may simply tare the balance after placing the weighing dish on the pan to determine the mass of each sample.
• To avoid congestion, assign one-half of the student groups to each mining site, then have them switch after they complete their three samples. Be sure students are recording the measurements in the correct place on the worksheet.
• Reinforce the concept that not all the mineral in a sample of ore can be feasibly or economically recovered by including a time limit. Once the students have spread out a sample, allow one minute to recover the minerals. One partner may recover the minerals using only forceps as the other partner keeps track of the time or the instructor may time all the groups together. Any metal pieces left in the large weighing dish represent unrecoverable metal.

Teacher Tips

• This activity is appropriate for an earth science study of minerals and mining and for reinforcing measurement.
• The type of mining simulated in this activity makes use of placers—loose nuggets of ore in gravel. Gold makes excellent placer deposits because it does not usually react with air or water. Silver, however, is rarely found as a placer deposit.
• The percent concentration of metals in this activity is highly inflated for student interest. Gold is sometimes mined when a ton of ore yields as little as 3 grams of the precious metal. In fact, precious metals and gems are usually expressed as grams per ton rather than percent concentration.
• To simulate the environmental impact of mining, provide chocolate chip cookies and have the students try to remove the chips with a toothpick and plastic spoon. They then must put the pieces of the cookie back as close to the original size and shape as possible.

Answers to Prelab Questions

1. The Flinn Copper Mine yields an average of 2.2 grams of copper from every 50 grams of ore. What is the percent concentration of copper in this mine?
   2.2 g Cu/50 g ore x 100 = 4.4% Cu
   
2. How much copper would be expected from one hundred grams of ore in the Flinn Copper Mine? From 1 kilogram of ore? Hint: 1 kg = 1000 g.
   100 g of ore would yield 4.4 g of copper
   
   {12992_Answers_Equation_3}
3. The expected profit from selling the copper extracted from the Flinn Copper Mine is $3 per 100 grams of copper. Use the previous information and Equation 2 to determine the copper profit value per kilogram of ore from the Flinn Copper Mine.
   {12992_PreLab_Equation_2}

Sample Data

Answers to Questions

Post-Activity Calculations

See Data Tables for sample answers.

Post-Lab Analysis

5. Calculate the profit per kilogram of ore mined at Site A using the same procedure from the Prelab Questions. First determine the average mass of each metal per kilogram of ore and record in Data Table 3. Then use the profit value for gold from the Activity Overview to determine the gold profit per kilogram of ore mined at Site A. Do the same for silver. Record these values in Data Table 3.

Sample calculations

6. Determine the gold and silver profit per kilogram of ore mined at Site B, respectively. Record in Data Table 3.
7. Calculate and record the total gold and silver profit per kilogram of ore mined at each site in Data Table 3.
8. Based on your calculations, which site would you recommend as the more profitable to mine? Mining site B would be more profitable to mine. On the average, more silver was obtained from site A than site B, but site B had more gold. Gold is much more profitable than silver.
9. Compare your results for Question 7 with other lab groups. Give two possible explanations for any differences you may find. How might these differences affect your recommendation? Note: The distribution of copper and aluminum in the gravel “ore” is not homogenous. If distributed according to the Prelab Preparation, the overall percent concentration for gold and silver at Site A should be 4.5 and 3, respectively, and 5.5 and 2 for site B. However, individual samples may vary widely. In testing, the percent concentration of gold from site A ranged from 6.3 to 8.2 and the silver ranged from 2.9 to 3.8. For site B, the percent of gold ranged from 5.8 to 9.3 and the range for silver was 1.2 to 2.3. Two trials showed that site A would be more profitable than site B, with an overall difference of only $2/kg ore between the sites. This would be a good opportunity to discuss consistency of results, reasons for variations, sample size and other factors that may influence mining a particular site.

References

Geology Project Homepage: http://www.unr.edu/sb204/geology/geology1.html (accessed February 2009).

Introduction

Precious metals have been discovered in a new location. Due to government regulations, your mining company is only able to buy the rights to one plot of land. Investigate samples from two different sites and determine which site would be the more profitable for the company to mine.

Concepts

• Percent concentration
• Ore
• Mineral extraction

Background

Minerals are usually found as compounds in rocks along with other materials. For example, galena is a mineral composed primarily of lead sulfide and sometimes contains a significant amount of silver sulfide. Galena is mined to obtain lead and silver. While most common minerals are found in the form of compounds (e.g., sulfides, oxides, silicates), some (e.g., gold, copper, silver) may be found in elemental form as free metals.

An ore is a rock deposit that contains enough valuable minerals from which metals may be mined at a profit. Once mineral deposits have been discovered, many factors are evaluated through a feasibility study to determine whether or not to mine the ore. Such considerations include the cost and safety factors of the physical and chemical processes used in separating minerals from ore as well as the environmental impact. The extent, market value, and accessibility of the ore are taken into account to determine how much of the desired mineral can be reasonably recovered.

The concentration of a desired metal within an ore deposit is often expressed as a percent concentration. The percent concentration may be calculated according to Equation 1.

For example, if 20 g of zinc were extracted from 200 g of ore, the percent concentration would be 10%. This means that for every 100 grams of ore, 10 grams of zinc may be extracted.

The percentage of metal in an ore is known as the grade of ore. The minimum grade of ore needed before a metal is considered for mining depends on the material. For example, zinc ore may call for at least an 8% concentration to make mining the metal profitable. Early copper mines yielded up to 88% copper, but today with better extraction techniques, ores with less than 1% copper are mined.

Experiment Overview

The purpose of this activity is to investigate samples of ore from two possible mining sites to determine the site that has the higher concentration of gold and silver. Based on this concentration, the more suitable site to set up a mining operation will be determined, assuming that the profit will be $350/100 g of metal for gold and $5/100 g of metal for silver.

Materials

Prelab Questions

1. The Flinn Copper Mine yields an average of 2.2 grams of copper from every 50 grams of ore. What is the percent concentration of copper in this mine?
2. How much copper would be expected from one hundred grams of ore in the Flinn Copper Mine? From 1 kilogram of ore.
   Hint: 1 kg = 1000 g.
3. The expected profit from selling the copper extracted from the Flinn Copper Mine is $3 per 100 grams of copper. Use the above information and Equation 2 to determine the copper profit value per kilogram of ore from the Flinn Copper Mine.
   {12992_PreLab_Equation_2}

Safety Precautions

The materials in this lab are considered nonhazardous. Use caution to avoid spilling the samples on the floor as spills may cause someone to slip and fall. Wash hands thoroughly with soap and water before leaving the laboratory. Please follow all laboratory safety guidelines.

Procedure

1. Obtain a sample of ore by filling a medicine cup from the proposed mining site (A or B) assigned by your instructor.
2. Mass a large weighing dish. Record this mass under the respective mining site (A or B) for sample 1 (mass of large dish) in Data Table 1 on the Minerals, Metals and Mining Worksheet.
3. Pour the ore from the medicine cup into the large weighing dish.
4. Mass the ore in the dish. Record the mass of the ore and the dish for sample 1 in Data Table 1.
5. Mass a small weighing dish. Record this mass for sample 1 in Data Table 1.
6. Using forceps, spread the ore out in the large weighing dish.
7. Using forceps, remove all the gold pieces from the ore and place them in the small weighing dish. Note: One partner may follow the same procedure starting with step 5 with a second small weighing dish and the silver pieces at the same time the other partner is removing the gold pieces.
8. Measure and record the mass of the gold and the dish.
9. Repeat steps 5–8 with a second small weighing dish and the silver pieces, recording data in the last three rows of Data Table 1.
10. Mix the gold and silver pieces back into the ore sample in the large weighing dish.
11. Return the ore sample to its original container and stir to mix. Note: Be sure the ore is returned to the correct mining site (A or B).
12. Repeat steps 1–11 two more times, recording the data for samples 2 and 3, respectively.
13. Repeat steps 1–12 with the ore from the other mining site (A or B).

Student Worksheet PDF

12992_Student1.pdf