ESSE1012_lab2_2024

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LE/ESSE 1012 3.0 The Earth Environment Winter 2024 Lab. Section: M Name: Sadaf Bayat Student Number: 219267475 LAB 2: MINERALS Due February 2, 2024, 10PM ET IMPORTANT: This is a hands-on lab. You must attend the lab session in person in order to receive credit for this lab. Unless otherwise indicated, show your work for all problems. You can either enter your answers into this document electronically using a computer or tablet, or you can print this document, handwrite your answers in the spaces provided, and scan the pages. If you need additional space, you can insert additional pages or you can add additional space within the Word document. For all numerical answers, the units should be indicated. Students can discuss this lab with each other, but copying from each other or copying from other sources is cheating and is not permitted. You should not share your answer sheets with other students or look at the answer sheets of other students. You should understand the concepts well enough to explain your answers in your own words. Your answers for hands-on portions of the lab should be based on work that you yourself performed in the lab location. If the lab procedure indicates that you can form groups to complete particular tasks, then you should still be physically present in the lab location contributing to the completion of those tasks, and you should write the names of other group members on your answer sheets. If your work relies on information that is obtained from a legitimate source other than ESSE 1012 course materials, please indicate the source of that information with enough detail so that someone else can locate the source. Please see the course outline for detailed policies. Although there are thousands of known minerals, over 99% of the rocks on Earth are made up of fewer than 20 minerals. In this laboratory exercise, you will examine the properties of these 'rock forming' minerals. The goal of this lab is to have you use the physical properties of crystalline solids to identify common rock forming minerals. In the process, you will use Tables A.1 and Table A.2 from the Jarvis text (available on eClass), along with the concepts covered in the lecture and Chapter 7 of the McConnell text . LE/ESSE 1012 Lab 2 - Winter 2024 ©NTandon Page 1 of 7

1. COLOUR, STREAK AND LUSTRE You are provided with the following samples: Mineral Name Lustre Pyrite Metallic Quartz Vitreous (glassy) Kaolinite Dull Earthy Talc Pearly Examine each sample and be sure that you can recognize each type of lustre before moving on. Use the streak plates (made of unglazed porcelain) along with your recently acquired knowledge of lustre to determine the colour, streak and lustre of the given minerals below. Non-Silicates: magnetite oolitic hematite limonite sphalerite galena pyrite Silicates: kaolinite amphibole garnet a) Complete the following table from your results (3 marks for each mineral) Mineral Colour Streak Lustre Magnetite (#71) Dark gray Black metalic Oolitic hematite (#75) Brown red brown dull earthy Limonite (#73) ton brown yellow brown dull earthy Sphalerite (#66) silver dark gray metalic Galena (#77) dark gray dark gray metalic Pyrite (#78) greenish gold greenish gold metalic Kaolinite (#82) white white dull earthy Amphibole (#62) gray nothing vitreous LE/ESSE 1012 Lab 2 - Winter 2024 ©NTandon Page 2 of 7

Garnet (#67) brown nothing vitreous b) Was streak colour useful for all of the minerals? Why or why not? If not, indicate the lustre(s) of the mineral(s) for which streak was not useful. Was there a particular group that streak was useful for? (4 marks) No it was not useful for all of the minerals. For vitreous lustre was not helpful because we could not see any thing at all. And the minerals are amphibole and garnet. Yes for dull earthy and and metallic it was helpful. c) Suppose that you encounter a rock sample with earthy lustre, and you wish to determine its mineral composition. One portion of the rock sample produces a reddish brown streak and another portion of the rock sample produces a yellowish brown streak. How would you interpret these results? (4 Marks) When one comes across a piece of earthy-colored rock, one can deduce the mineral composition based on the different hues of the streaks. Oolitic hematite (#75), a brown- colored mineral with a reddish-brown streak and a dull, earthy luster, is most likely the section of the sample that produced this pattern. Similar to limonite (#73), which likewise has a dull earthy luster and a ton brown tint, the yellowish-brown streak seen in another area of the rock sample matches its characteristics. According to the interpretation, the rock sample may contain minerals like limonite and oolitic hematite, which both have an earthy luster with matching streak hues. It is recommended that additional analysis be carried out, including mineral assays for a more accurate determination of the rock sample's mineral makeup. d) Pyrite is commonly known as “fool’s gold” because it has some physical properties similar to gold. Give two different physical properties that you would use to identify pyrite as distinct from gold? (4 Marks) Because pyrite, also referred to as "fool's gold," resembles gold in some visual aspects, it is important to distinguish it by its unique physical characteristics. Their different colors are one of the main things that set them apart. Whereas pyrite usually has a lighter, brassier yellow color, gold has a rich, deep yellow hue. Even though it is slight, this variation in pigment is an important feature to consider when evaluating the minerals visually. Another useful technique for distinction is to take the minerals' hardness into account. Pyrite is noticeably tougher than gold, which is rather delicate and easily scraped with a fingernail or knife. A basic hardness test can be used to determine this difference, since pyrite is harder and gold is more prone to scratches. One can confidently distinguish pyrite from gold by closely scrutinizing both color and hardness, and so avoid the misunderstanding that pyrite is "fool's gold." LE/ESSE 1012 Lab 2 - Winter 2024 ©NTandon Page 3 of 7

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2. HARDNESS You have been provided with 5 of the 10 minerals in the Mohs’ hardness scale. In increasing order of hardness you will find: 1 – Talc 7 – Quartz 3 – Calcite 9 – Corundum 4 – Fluorite a) Using the above minerals, determine the hardness bounds of a copper coin. Explain your approach. (4 marks) Using the above minerals and the Mohs hardness scale, we may calculate the boundaries of a copper coin's hardness. On the scale, 1 represents the softest material (talc), and 10 represents the hardest material (diamond). The minerals that are pertinent in this instance are fluorite (4), calcite (3), and talc (1). It is clear by looking at the scale that fluorite is even harder than calcite, talc is the softest material, and calcite is slightly harder. As a result, a copper coin's hardness limits are between talc (1) and calcite (3). The foundation of this method is the idea that any mineral with a greater hardness value can scratch any mineral with a lower hardness value, and vice versa. As a result, this research enables us to determine the hardness of the copper coin on the Mohs' scale with a fair degree of accuracy. b) The hardness of glass changes with its chemical composition. Determine the approximate hardness of the glass plate provided in the lab. (4 Marks) We can use the Mohs' hardness scale as a guide to determine the approximate hardness of the glass plate provided in the lab. This scale, which goes from 1 (softest) to 10 (hardest), classifies minerals according to how resistant they are to scratches. Glass is typically rated between 5.5 and 6.5 on the Mohs' scale due to its varied hardness based on its chemical makeup. Based on the comparison of this data with known minerals, one can reasonably infer that the glass plate has a Mohs hardness of approximately 6. This puts the glass plate in the range of hardness between orthoclase (6) and feldspar (6), which are frequent minerals in glass compositions. It's important to understand that the exact hardness might change based on the glass's unique chemical makeup. This estimate is a helpful point of reference for comprehending the glass plate's scratch resistance in a lab setting. c) If you had a sample of what you believe is fluorite, how would you identify it? (4 Marks) If a sample exhibits a wide spectrum of colors, such as purple, blue, green, yellow, or clear tones, it is likely fluorite. Examine transparency because fluorite is usually either translucent or transparent. Upon breaking, look for the distinctive octahedral cleavage of the material. One distinguishing characteristic is fluorescence, which appears as blue or green when exposed to UV light. Verify the hardness with a straightforward scratch test. It is rated at 4 on the Mohs scale. Since fluorite has a rather high density, consider density. Comprehensive identification is made possible by a combination of these characteristics, which include color, transparency, cleavage, fluorescence, hardness, and density. Advanced methods such as chemical analysis or X-ray diffraction can offer additional validation if necessary. 3. CLEAVAGE Examine your mineral specimens to observe the physical property known as cleavage. a) Why is cleavage an important physical property? (4 Marks) Because it helps identify minerals and offers insights into crystal structure and geological LE/ESSE 1012 Lab 2 - Winter 2024 ©NTandon Page 4 of 7

processes, cleavage is an important physical characteristic in mineralogy. Each mineral has a unique way of breaking along different planes that helps to set it apart from other minerals. The internal arrangement of atoms in the crystal lattice is reflected in the cleavage pattern, which provides important information on the composition of the mineral. Evaluating cleavage is also essential for assessing a mineral specimen's quality and for real-world uses in the mining industry, where minerals with advantageous cleavage qualities are easier to process. All things considered, cleavage is an essential tool for comprehending minerals, their production, and their industrial significance. b) How does cleavage originate in minerals? (4 Marks) The internal atomic structure and the planes of weakness inside the crystal lattice are the sources of cleavage in minerals. It is caused by how the atoms are arranged in the crystal structure of the mineral and the forces holding them together. In contrast to other orientations, cleavage happens along the planes of weakest atomic bonds, where the cohesive forces between atoms are weaker. These planes of weakness are dictated by the atomic arrangement and symmetry of the mineral and are usually aligned with particular crystallographic directions. The mineral has a tendency to fracture along these preset planes when an external force or stress is applied, producing smooth, flat surfaces that are indicative of cleavage. Each type of mineral has a different number and direction of cleavage planes, which act as a unique fingerprint to help with categorization and identification. A mineral specimen's cleavage, if present and of high quality, can provide important information on the internal structure and formation environment of the material. c) Explain in your own words why mica does not have three directions of cleavage (a diagram might help with your explanation). (4 Marks) Since its cleavage planes are limited to one direction, mica, a mineral with a sheet-like crystal structure, does not cleave in three directions. Mica's particular crystal lattice structure causes its cleavage to occur parallel to a single plane, in contrast to minerals with three orientations of cleavage, such calcite or halite, which break into separate three-dimensional patterns. Imagine a stack of sheets; the crystal structure of mica is made up of layers that are bonded together by tiny forces. Thin, flexible sheets are produced when cleavage happens along the plane that separates these layers. An illustration of this could be this: Imagine that the cleavage is parallel to a row of flat sheets that are piled one on top of the other. Mica differs from other minerals with three-dimensional cleavage patterns due to its distinctive flaky appearance and flexibility, which are caused by its single-direction cleavage. d) Suppose a mineral has three directions of cleavage (e.g., calcite). How many faces will a crystal of the mineral have? Why? (4 Marks) A mineral with three cleavage directions will have six faces in its crystal. This is due to the fact that minerals that cleave in three directions usually crystallize into rhombohedra or hexagonal prisms. The number of cleavage planes on a crystal indicates how many faces it contains. Every plane of cleavage corresponds to a level surface within the crystal. The crystal would have three sets of parallel faces, one for each of the three cleavage directions, for a total of six faces in the case of three cleavage directions. One of the most important features utilized in the identification and classification of minerals is the geometric arrangement of these faces, which also adds to the LE/ESSE 1012 Lab 2 - Winter 2024 ©NTandon Page 5 of 7

overall shape of the crystal. 4. MINERAL IDENTIFICATION You are provided with ten unknown minerals. Using concepts covered in the lecture notes and other course materials, identify all of these minerals. Complete the following table. For each mineral, list only the diagnostic properties (not every property) that you used to identify it. Use the following format (3 marks for each mineral): Mineral # Mineral Name Main Diagnostic Properties U1 hornblende Cleavage in two directions dark color, prismatic crystals. U2 garnet conchoidal fracture and can absorb magnet U3 potasium feldspar hardness around 6, pink U4 quartz Brass-yellow color, metallic luster U6 chalcopyrite Brass-yellow color, metallic luster U8 biotite Perfect cleavage in one direction, dark brown to black color U9 muscovite light-colored, transparent to translucent U10 magnetide Black color, strong magnetism, metallic luster 5. EXAMINATION OF AN IGNEOUS ROCK Examine the igneous rock sample provided in the lab and answer the following questions a) Are there any visible features that make clear that the rock you are examining is an igneous rock rather than a metamorphic rock? If so what are they? (3 Marks) Metamorphic rocks are folded/layered, compacted, and frequently crystalline in form, whereas igneous rocks are speckled with big visible crystals or particles. Upon closer inspection of the rock samples, I saw that one of them had visible crystals scattered throughout the rock. b) Identify two felsic minerals in the sample. What features did you notice in order to identify these minerals? (3 Marks) White-colored, vitreous lustrous Plagioclase Feldspar potassium Feldspar: Salmon or pink in color, vitreous lustre LE/ESSE 1012 Lab 2 - Winter 2024 ©NTandon Page 6 of 7

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c) Identify one mafic mineral in the sample. What feature(s) did you notice in order to identify this mineral? (3 Marks) Mafic minerals are high in iron and magnesium and usually have a dark color. Among the common mafic minerals are pyroxene, hornblende, and biotite. LE/ESSE 1012 Lab 2 - Winter 2024 ©NTandon Page 7 of 7

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