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 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. 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, satiny, 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 M221, M223, and M225. 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 four minerals for hardness. What is the hardness of quartz?
5. Describe the lustre of the samples.
6. What is a diagnostic property of quartz?
7. Sample M225 is flint, an example of microcrystalline quartz that is always grey to black in colour. Do the diagnostic properties for quartz apply to flint as well?
Feldspars
| Sample M201 | Mineral name: |
| Sample M202 | Mineral name: |
| Sample M211 | 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 (albite). 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.
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 M202 | Hardness: |
| Sample M211 | Hardness: |
2. Describe the cleavage exhibited by these samples:
3. Looking at M201 and M211, do either of these samples exhibit striations? Do either of the samples exhibit iridescence?
4. How can you distinguish between K-feldspar and plagioclase feldspar?
Silicate Mineral Group: Sheet Silicates (phyllosilicates)
| Sample M121 | Mineral name: |
| Sample M271 | 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 muscovite and biotite?
| Sample M281 | Mineral name: |
5. What is the hardness of the sample?
6. Describe the lustre of this mineral:
7. What is a diagnostic property of talc?
| Sample M291 | Mineral name: |
8. Describe the lustre of this mineral:
9. What is a diagnostic property of kaolinite?
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 pyroxene:
2. What is the colour of this mineral?
3. What is a diagnostic property of pyroxene?
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 hornblende:
2. What is the colour of this mineral?
3. What is a diagnostic property of hornblende?
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. Do you see any crystal faces on your sample?
2. What is the hardness of the sample?
3. What is the lustre of garnet?
4. What is a diagnostic property of garnet?
| Sample M301 | Mineral name: |
Olivine is an igneous mineral that is green, one of the few minerals that can be identified by colour. 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 olivine?
6. Describe the feel of the sample:
7. What is a diagnostic property of olivine?
A mineral that includes silica tetrahedra.
The lustre of a mineral into which light does penetrate.
Feldspar with the formula KAlSi3O8.
wavy, irregular ‘veiny’ lines that may appear as a slightly different colour than the rest of the feldspar crystal (e.g., paler pink, cloudy more opaque white)
Sodium-rich plagioclase feldspar.
a growth pattern that looks like a set of hairline grooves or faint parallel lines, visible on crystal faces of some minerals
A very common family of framework silicate minerals.
A single chain silicate mineral.
A double-chain ferromagnesian silicate mineral (e.g., hornblende).
