Lab 2 Exercises

The exercises below will guide you through the mineral samples in Mineral Kits 1 and 2. Review the physical properties of minerals presented in Chapter 2.3 before you begin these exercises. You may wish to consult the mineral identification tables at the back of this manual as you complete the exercises below.

Part I: Cleavage and Fracture

The minerals in this part include a mix of silicate and non-silicate minerals found in Mineral Kits 1 and 2.

1. Do the following samples exhibit cleavage or fracture? If the sample exhibits cleavage, specify the number of cleavage planes and approximate angle between them.

2. What is the difference between a crystal face and a cleavage plane?

3. Look at sample M202(S). This is a good example of a mineral with 2 cleavages at almost right angles to each other. Select two other samples that also demonstrate this type of cleavage.

4. Now select a sample which also appears to have a least two cleavages but with the cleavage surfaces oblique (at some angle other than 90°) to each other.

5. Which sample has one (perfect) cleavage only?

6. Look at the fractured surface of sample M225. Try to describe this surface (rough? curved? splintery? etc.). This is an example of conchoidal fracture. Does this sample exhibit any cleavage?

7. What other sample also exhibits conchoidal fracture?

Part II: Non-silicate Minerals

Certain physical properties are diagnostic for a particular mineral. These diagnostic properties will help you distinguish a particular mineral. The questions below will help you identify these diagnostic properties. Remember: you must be able to identify all the physical properties of each mineral, not just the diagnostic properties. You should also know the group to which each mineral belongs (e.g., sulphides, oxides).

Mineral Group: Native Elements

1. Does this mineral exhibit cleavage?                If yes, describe the cleavage:                                          
2. What is the approximate hardness of the sample on the Mohs scale of hardness?                  
3. What is the specific gravity of the sample (high, medium or low)?

4. Describe the lustre of this mineral:                                                                                    

5. Describe the streak:                                                                                    

6. What is a diagnostic property of graphite?

Mineral Group: Oxides

1. Do any of these samples exhibit cleavage?                  
2. If yes, which one? Describe the cleavage:                                          
3. Looking at samples M51/52 and M53, what is the lustre of each sample?

4. Compare the streak of each sample. Describe what you see:

5. Do any of the samples attract a magnet? Which one?                                          
6. What is the diagnostic property of magnetite?

7. What is the diagnostic property of hematite?

Mineral Group: Carbonates

1. Does this mineral exhibit cleavage?                    If so, describe the cleavage:                                          
2. What is the approximate hardness of the sample on the Mohs scale of hardness?                   
3. Describe the lustre of this mineral.

4. Does the sample react to a drop of HCl?                
5. What is a diagnostic property of calcite?

Mineral Group: Sulphides

1. What do all these minerals have in common?

2. Test all four minerals for hardness. Do any of these minerals scratch the glass plate?                                                                                    
3. Which is harder pyrite or chalcopyrite?                                                                                    
4. Describe the streak of sphalerite:

5. What is the lustre of pyrite, chalcopyrite and galena?                                                                                    
6. What is the lustre of sphalerite?                                                                                    
7. Which mineral has the highest specific gravity?                                                                                    
8. Do you see cleavage faces on any of these minerals?                                                                                    
9. How can you tell pyrite from chalcopyrite?

10. What is a diagnostic property of galena?

11. What is a diagnostic property of sphalerite?

12. Many sulphide minerals contain valuable ore metals that are used to manufacture the objects and technology you use every day. Using Appendix 4 as a guide, complete the table below.

13. Name two economic uses for the mineral galena.

14. Explain the steps involved in extracting galena from an ore deposit and eventually producing pure lead metal.

Mineral Group: Sulphates

1. What is the approximate hardness of this mineral?                                          
2. Describe the lustre of this mineral:                                                                                    

3. What is the diagnostic property of gypsum?

4. What is the main economic use for gypsum and where is the world’s most productive gypsum mining area?

Mineral Group: Halides

1. Describe the cleavage of each sample.

2. What is the approximate hardness of the two minerals on the Mohs scale of hardness?

3. Compare the specific gravity of the two minerals. Which is higher?                                          
4. What is a diagnostic property of halite?

5. What is a diagnostic property of fluorite?

6. How can you distinguish fluorite from quartz? Quartz is a silicate mineral that will be studied in Lab 3.