GEO109_SCI210_Lab 1_Observing Minerals SP22

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University of Dayton *

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Geology

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Apr 3, 2024

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GEO 109L – Earth, Environment, & Society Lab SCI 210L – The Dynamic Earth Lab Lab Exercise 1: Observing Earth’s Minerals Lab Exercise On your table is a box of fifteen mineral samples. These are the samples that you will observe and identify in lab next week. For this week, you will observe the major physical properties and practice using the tools to test these properties. As you work with the samples, think about how a particular property helps us understand minerals and distinguish different types of minerals from each other. Properties of Color and Light - Color and Streak Color of a specific mineral sample is determined by the way in which light is absorbed by that sample. The color of a specific mineral type can vary greatly depending on the chemical composition and the purity of the mineral structure. While the great variety of colors that are possible for just one type of mineral makes it sometimes difficult to use color as a primary tool in identifying a sample, it is still important to observe. It is the most recognizable property of a sample and one that can be observed with just your naked eye. The streak color of a mineral is observed after dragging a sample across an unglazed porcelain plate (a streak plate). By dragging a sample across a streak plate you are slightly pulverizing the sample into a fine powder and THEN observing the color of the powder. This does not necessarily mean that the streak color will always be the same as the color of the hand sample. In fact, the streak is at times a more reliable indicator of a mineral identification. 1) Pick up a piece of samples 2, 3, 12, and 13. Each person in your group can work with one of these samples. Observe the color and the streak for each sample and record below. Sample Number a) Color of sample b) Color of Streak 2 3 12 13 2) Why do you think it is necessary to observe both color and streak for a mineral sample? Explain. Properties of Light and Color – Luster The luster of a mineral is the way in which light is reflected off the mineral’s surface. Think about how you describe the 'shininess' of things in your everyday life. How would you describe them? A piece of glass would be glassy. A quarter is metallic. A piece of wood is dull. A CD is iridescent. These are the same types of terms that you can use to describe the luster of minerals. It is important to note that all minerals can first be broken down in to two main categories based on their luster: METALLIC & NON-METALLIC . Lab 1 | 1 NAME: ______________________ Table # _____
Note: Non-metallic minerals are further described with a specific luster type (See luster handout on your table). 3) Use the luster information provided on your table to help you describe the luster of the following four minerals. Again, each person at your table can work with one of the samples and then share your observations with your group. Sample Number a) Color b) Luster (Metallic M or Non-Metallic NM ) c) Only if Non-metallic (NM), give a specific NM luster type (See Handout). 1 6 11 14 Mineral Structure Properties – Electrical Conductivity 4) Another property that can be used to determine if a mineral is metallic is its ability to conduct electricity. Using a piece of sample #3, complete the electrical connection on the back of the flashlight with a small piece of the mineral. Record what happens below. Mineral Structure Properties – Hardness Hardness is described as the mineral surface’s resistance to scratching. It is measured on a relative scale of index minerals, called the Moh’s scale (see handout on table). Hand samples of minerals can be tested using a set of common tools that match given values on the Moh's scale. For the glass plate, scratch the mineral on the plate to see if the mineral is harder than the plate. For the other testing materials, use them to try to scratch the mineral and see which is harder. 5) Use the tools provided and determine the range for the hardness value (number) for each of the four samples listed. Use the table on the back of the Mineral ID handout as a guide. Record your answer for each sample by placing one check in the box that best represents the range of hardness for that sample. Sample Number < 2.5 2.5 – 3.5 3.5 – 4.5 4.5 – 5.5 > 5.5 5 8 10 12 2
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