Chapter2 Exercises GEO LAB.docx

Chapter 2: Minerals 2-E1 | 1 Chapter 2: Minerals Adapted by Lyndsay R. Hauber & Joyce M. McBeth (2018) University of Saskatchewan from Deline B, Harris R & Tefend K. (2015) "Laboratory Manual for Introductory Geology". First Edition. Chapter 7 "Minerals" by Randa Harris, CC BY-SA 4.0. Last edited: 8 Jan 2020 Note: much of the overview material for this chapter is replicated in this exercise section for your reference as you complete the lab. Your name: NSID and Student number: Date and lab section time: _ TAs' names: Your TAs will check that you have completed the questions correctly at the end of the lab period. Please hold on to your lab notes to help you prepare for the rock and mineral quiz and your lab final exam. Overview of minerals 2.2PHYSICAL PROPERTIES Identifying a mineral is a little like playing detective. Minerals are identified by their physical properties. How would you describe the mineral in Figure 2.2? You may say that it is shiny, gold, and has a particular shape. Each of these descriptions is a physical property (shiny is lustre, gold is colour, shape is crystal form). Physical properties can vary within the same minerals, so caution should be applied when identifying minerals. For example, colour is a property that is not a very realistic diagnostic tool in many cases, as some minerals, such as Quartz, can come in a variety of colours (e.g. Figure 2.3). Occasionally, colour can be helpful, as in

Chapter 2: Minerals 2-E1 | 2 Figure 2.2 | Describe this mineral. Source: Randa Harris (2015) CC BY-SA 3.0 the case of olivine, which is said to be “olive green”, a light to dark green (e.g. Figure 2.4). We will cover each of the physical properties in detail to help you identify the minerals.

Chapter 2: Minerals 2-E1 | 3 Figure 2.3 | Examples of the different varieties of quartz (jasper, rose quartz, smoky quartz, agate, amethyst, citrine, and petrified wood), demonstrating the difficulty of identifying this mineral. Source: Randa Harris (201) CC BY-SA 3.0 Figure 2.4 | The mineral olivine has an "olive green" colour. Source: Joyce M. McBeth (2018) CC BY 4.0 2.2.1 Hardness Hardness refers to the resistance of a mineral to being scratched by a different mineral or material and is a product of the strength of the bonds between the atoms of a mineral.

Chapter 2: Minerals 2-E1 | 4 Whatever substance does the scratching is harder and the item scratched is softer. Hardness is based off a scale of 1 to

Chapter 2: Minerals 2-E1 | 5 10 created by a mineralogist named Friedrich Mohs (Figure 2.5). Mohs’ scale lists ten minerals in order of relative hardness, with each mineral on the scale able to scratch a mineral of lower number. Figure 2.5 | Mohs Scale of Hardness. Note that the hardness of a steel nail will vary depending on the kind of steel. Source: Randa Harris (2015) CC-BY 3.0 Your mineral kit comes with several items of a known hardness. The glass plate has a hardness of 5.5, the iron nail has a hardness of 4, the copper coin has a hardness of 3, and your fingernail has a hardness of 2.5. If you can scratch a mineral, then it would be softer than your fingernail, so therefore its hardness would be <2.5. When trying to scratch a surface, use force, but be cautious with the glass plate. ALWAYS lay the glass plate on a flat surface rather than holding it in your hand in case it breaks. Do not confuse mineral powder with a scratch – use your finger to feel for a Figure 2.6 | An example of a scratch made by the mineral quartz on a streak

Chapter 2: Minerals 2-E1 | 6 plate. The red arrow is pointing to the scratch. Quartz, therefore, is harder than glass. Source: Randa Harris (2015) CC BY-SA 3.0 Figure 2.7 | An example of a scratch made by a fingernail on the mineral gypsum. The red arrow is pointing to the scratch. Gypsum, therefore, is softer than a fingernail. Source: Randa Harris (2015) CC BY-SA 3.0

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