Lab 3 Exercises
The exercises below will guide you through the silicate mineral samples in Mineral Kits 1 and 2. Review the physical properties of minerals presented in Lab 2 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. Note that all silicate minerals have non-metallic lustre. As you are observing the following samples keep in mind you have to classify the lustre using more descriptive terms such as vitreous, earthy or dull, pearly etc. Remember: you must be able to identify all the physical properties of each mineral, not just the diagnostic properties.
Silicate Mineral Group: Framework Silicates
1. Examine samples M225, M221, and M223. All of these samples are varieties of the same mineral. Name the mineral:
2. Describe the cleavage or fracture exhibited in these samples:
3. How can you distinguish between a cleavage plane and a crystal face?
4. Test all three minerals for hardness. Does each mineral have the same hardness? If so, what is it?
5. Describe the lustre of the samples.
6. What is a diagnostic property of the mineral associated with sample M221?
7. While sample M225 technically has the same mineral formula as samples M221 and M223, it looks very different. Do the diagnostic properties of M221 and M223 apply to M225 as well?
Feldspars
| Sample M211 | Mineral name: |
| Sample M201 | Mineral name: |
| Sample M202 | Mineral name: |
You have a pink/salmon coloured sample and a white sample of potassium feldspar (K-feldspar). A pink feldspar will always be K-feldspar, and may show exsolution lamellae. A white feldspar may be K-feldspar or plagioclase feldspar. If you have a white K-feldspar and a white plagioclase feldspar look for striations on the plagioclase feldspar and that will differentiate them. The dark plagioclase feldspar (labradorite) will exhibit striations and has diagnostic iridescence (also sometimes called “labradorescence”).
1. Examine all your K-feldspar and plagioclase feldspars. These minerals are all feldspars, however, we will refer to them by their mineral names and classify them as framework silicates. Test each sample for hardness:
| Sample M201 | Hardness: |
| Sample M211 | Hardness: |
| Sample M202 | Hardness: |
2. Describe the cleavage exhibited by these samples:
3. Looking at M202 and M211, do either of these samples exhibit striations? Based on what you know, do you think that either of these samples might be labradorite?
4. How can you distinguish between potassium feldspar and plagioclase feldspar?
Silicate Mineral Group: Sheet Silicates (phyllosilicates)
| Sample M271 | Mineral name: |
| Sample M121 | Mineral name: |
1. Describe the cleavage of these two minerals:
2. What is the hardness of these two minerals?
3. What is a diagnostic property of mica minerals?
4. How can you distinguish between these two minerals?
| Sample M281 | Mineral name: |
5. What is the hardness of the sample?
6. Describe the lustre of this mineral:
7. Describe the cleavage of this mineral:
8. What is a diagnostic property of this mineral?
| Sample M291 | Mineral name: |
9. Describe the lustre of this mineral:
10. Describe the cleavage of this mineral:
11. What is a diagnostic property of this mineral?
Silicate Mineral Group: Single Chain Silicates
Single chain silicates include the pyroxene family of minerals. There is one pyroxene (augite) in the mineral kit and the samples vary in colour.
| Sample M101 | Mineral name: |
1. Describe the cleavage of the this mineral:
2. What is the colour of this mineral?
3. What is a diagnostic property of this mineral?
Silicate Mineral Group: Double Chain Silicates
Double chain silicates include the amphibole family of minerals. There is one amphibole (hornblende) in the mineral kit and the samples vary in colour.
| Sample M111 | Mineral name: |
1. Describe the cleavage of this mineral:
2. What is the colour of this mineral?
3. What is a diagnostic property of this mineral?
Silicate Mineral Group: Isolated Silicates
| Sample M131 | Mineral name: |
The garnet family also contains various kinds of garnet. The most common is almandine, a dark ruby red coloured garnet.
1. Describe the cleavage/fracture of this sample. Do you see any crystal faces?
2. What is the hardness of the sample?
3. What is the lustre of this sample?
4. What is a diagnostic property of this sample?
| Sample M301 | Mineral name: |
Olivine is an igneous mineral that is commonly green. The samples of olivine in your kit are actually samples of an ultramafic igneous rock composed of many small crystals of olivine.
5. What is the hardness of the olivine?
6. Describe the feel of the sample:
7. What is a diagnostic property of the olivine?
