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 the lab introduction lecture 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? Explain how you might determine whether you were looking at a crystal face and a cleavage plane if you stumbled upon a well-exposed mineral in the field.

3. Look at sample M211. This is a good example of a mineral with 2 cleavages at almost right angles to each other. Select two other samples that demonstrate this type of cleavage.

4. 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. Describe the sample (use your answers from Question 1 as a guide).

5. Is there a sample that has one (perfect) cleavage only? If so, list it below.

6. Look at the fractured surface of sample M31. Try to describe this surface (rough? curved? splintery? etc.). This is an example of uneven fracture. Does this sample exhibit any cleavage?

7. List one of the other samples that shows uneven 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 this mineral?

Mineral Group: Oxides

1. Do any of these samples exhibit cleavage?                  
2. If yes, which one? Describe the cleavage:                                          
3. Looking at samples M11/M12 and M51/M52, 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 the mineral associated with M11/M12?

7. What is the diagnostic property of the mineral associated with M51/M52?

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 this mineral?

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: M31, or M41/M42?                                                                                    
4. Describe the streak of M141:

5. What is the lustre of M31, M41/M42, and M1?                                                                                    
6. What is the lustre of M141?                                                                                    
7. Which mineral has the highest specific gravity?                                                                                    
8. Do you see cleavage faces on any of these minerals?                                                                                    
9. Describe the differences between M31 and M41/M42.

10. What is a diagnostic property of the mineral associated with M1/M2?

11. What is a diagnostic property of the mineral associated with M141?

12. Many sulphide minerals contain valuable ore metals that are used to manufacture the objects and technology you use every day. Using the internet (as well as your instructor) as a guide, complete the table below.

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 this mineral?

4. What is the main economic use for this mineral? Hint: you may need to consult the internet (or your instructor) to answer this question.

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 M231 and M261. Which is higher?                                          
4. What is a diagnostic property of the mineral associated with M231?

5. What is a diagnostic property of the mineral associated with M261?

6. How can you distinguish the mineral associated with M261 from quartz? Quartz is a silicate mineral that will be studied in Lab 3.