Minerals Lab 1 - S24 (1)
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Colorado State University, Fort Collins *
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Course
121
Subject
Geology
Date
Apr 3, 2024
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8
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GEOL 121 Name_____________________________- Lab Section__________________ 1 MINERALS LAB 1
Learning Objectives At the end of this lab students will be able to: 1. Observe characteristics of minerals, including color, streak, luster, magnetism, reaction to acid, cleavage and fracture, hardness, and density. 2. Describe differences in physical properties of minerals. Introduction Ultimately, geology is about storytelling; we can think of the entire Earth’s history as a book, the pages in the book are filled with stories that we developed by looking at the rocks that form our planet. Minerals that make up those rocks help us identify the rocks, so we can tell their stories. We also use minerals in our lives every day, often without even noticing. Minerals are in your cell phone, your car, your countertops (well, some of our countertops anyway) and even your walls. So, not only do minerals help us tell Earth’s story but they also help make our modern lives possible. Minerals come in all shapes, colors, and sizes but they share common characteristics that we can use to sort them into groups. In this lab, you take on the role of a mineralogist by making observations and testing various physical properties of unknown minerals.
Mineral Mystery Lab GEOL 121
2 Step 1: Search for clues Observe the set of minerals in front of you. None of them are currently named - that’s okay! Before we get into labeling, let’s take a close look at each of the minerals. Q1
. What are some physical characteristics that multiple minerals share? What are three different ways that you could divide these minerals into 2–3 groups based on those characteristics? Option 1 Group 1 characteristic: Group 2 characteristic: Group 3 characteristic (optional): Mineral(s): Mineral(s): Mineral(s): Option 2 Group 1 characteristic: Group 2 characteristic: Group 3 characteristic (optional): Mineral(s): Mineral(s): Mineral(s): Option 3 Group 1 characteristic: Group 2 characteristic: Group 3 characteristic (optional): Mineral(s): Mineral(s): Mineral(s): Once you have come up with three different ways to divide these minerals into groups based on their physical characteristics, compare the groups you made with the other pair of students in your small group. What groups are the same? What groups are different? Is there more than one valid way to group the minerals?
Mineral Mystery Lab GEOL 121
3 Step 2: Observing the Properties of Minerals Each of the table groups is set up as a station examining one or two specific properties of minerals. Rotate through the stations to identify each property for your 12 minerals. When you are finished with all stations check in with your TA for the Demonstration of Understanding. Station 1: Color and Streak Color is among the more obvious qualities of a mineral, yet the color of a mineral may vary considerably depending on slight variations in chemical composition. Some chemical elements can create strong color effects, even when they are present only as trace impurities. Streak is the color of the fine powder of a mineral. Streak is observed by rubbing the mineral across a piece of unglazed porcelain known as a streak plate. Many minerals leave a streak of powder with a diagnostic color. Thus, streak is commonly more reliable than the color of the mineral itself. Use the example kits to investigate mineral color and streak. Then describe the color and streak of each of the unknown minerals. Color Streak Color Streak Mineral A Mineral G Mineral B Mineral H Mineral C Mineral I Mineral D Mineral J Mineral E Mineral K Mineral F Mineral L
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Mineral Mystery Lab GEOL 121
4 Station 2: Luster Luster describes the way light reflects off a mineral. Minerals are generally grouped into two categories: metallic and non-metallic. If the light reflecting off the mineral looks like metal it is metallic. If the light does not look metallic the mineral’s luster may be considered vitreous (like glass), pearly, earthy/dull, waxy, or silky. Use the example kits to investigate the different types of mineral luster. Then describe the luster of each of the unknown minerals. Metallic (y/n) Metallic (y/n) Mineral A Mineral G Mineral B Mineral H Mineral C Mineral I Mineral D Mineral J Mineral E Mineral K Mineral F Mineral L
Mineral Mystery Lab GEOL 121
5 Station 3: Magnetism and Acid Test Most mineral are not magnetic at all, but iron-bearing minerals often exhibit the property of magnetism. Some are strongly magnetic and some weakly magnetic. To test for magnetism, use a magnet and slowly bring the magnet in the vicinity of the mineral. You should be able to feel the suspended magnet’s attraction (or not) to the mineral. Carbonate minerals (those containing the anion (CO
3
)
2-
) will effervesce (fizz/form bubbles) when a drop of dilute hydrochloric acid (HCl) is applied to a freshly exposed surface. The fizzing is the release of CO
2
gas, the same gas that is released when you pop the top of a soda bottle. Magnetic (y/n) Reacts with acid (y/n) Magnetic (y/n) Reacts with acid (y/n) Mineral A Mineral G Mineral B Mineral H Mineral C Mineral I Mineral D Mineral J Mineral E Mineral K Mineral F Mineral L
Mineral Mystery Lab GEOL 121
6 Station 4: Cleavage and Fracture Cleavage and fracture refer to the way minerals break. Cleavage is the tendency of some minerals to break along plane of weakness in the mineral’s crystalline structure. If breaking a mineral leaves behind relatively flat surfaces that give off flashes of reflected light when the hand sample is rotated, the mineral has cleavage. These cleavage surfaces are the planes of weakness. Fracture occurs when a mineral breaks but not along cleavage planes. Many minerals fracture because they have no planes of weak bonds in their atomic structure. In these cases, fractures still can form characteristic shapes or patterns. For example, conchoidal fracture creates smooth and curved surfaces, similar to a clam shell. Some minerals break into splintery or fibrous fragments. Others fracture into irregular shapes. Use the example kits to investigate mineral cleavage and fracture. Then determine the number and angle of cleavage planes present in each of the unknown minerals. If no cleavage planes are present, describe fracture of the unknown mineral. Number and angle of cleavage planes. If 0, describe fracture. Number and angle of cleavage planes. If 0, describe fracture Mineral A Mineral G Mineral B Mineral H Mineral C Mineral I Mineral D Mineral J Mineral E Mineral K Mineral F Mineral L
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Mineral Mystery Lab GEOL 121
7 Station 5: Hardness Hardness is the resistance of a mineral to scratching. The physical property of hardness is determined by crystal structure and strength of the bonds between atoms. Generally, the stronger the chemical bonds, the harder the mineral. Minerals come in a wide range of hardness. To compare them, geologists use the Mohs Hardness Scale. On this relative scale , each mineral is harder compared to all those with lower numbers on the scale. For example, 10 (diamond) is the hardest and so will scratch every mineral listed down to 1 (talc), which is the softest. Using this information, a range of hardness is determined. For example, a mineral that can be scratched by quartz but not by potassium feldspar has a hardness range between 6 and 7 on Mohs. Scratched by fingernail (y/n) Scratched by penny (y/n) Scratched by glass plate (y/n) Scratched by nail (y/n) Hardness Mineral A Mineral B Mineral C Mineral D Mineral E Mineral F Mineral G Mineral H Mineral I Mineral J Mineral K Mineral L
Mineral Mystery Lab GEOL 121
8 Station 6: Density An important physical property of a mineral is how light or heavy it feels relative to the size of the sample; its heft. The property that causes this observed difference is density, which is mass per unit volume. Minerals with a high density, such as gold, have closely packed atoms. Minerals with a low density, such as ice, have loosely packed atoms. The density of minerals is often reported as specific gravity (S.G.), the density of a substance relative to that of an equal volume of water. The most common silicate minerals have densities in the range of 2.5-3.0 g/cm
3
or 2.5-3 times that of water. Minerals made of metallic elements have higher densities. You will measure the mass of each sample using the scale. To measure volume, you will place the sample in a cylinder of water and measure the change in water level. The change in water level in mL is equal to the volume of the sample in cm
3
. Density is equal to mass divided by volume. Mass (g) Volume (cm
3
) Density (g/cm
3
) Mineral A Mineral B Mineral C Mineral D Mineral E Mineral F Mineral G Mineral H Mineral I Mineral J Mineral K Mineral L