The Study of Minerals (Chapter 1) Introduction to Mineral Identification THE SILICATE MINERALS

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1 GEOLOGY 306 Laboratory Instructor: TERRY J. BOROUGHS NAME: The Study of Minerals (Chapter 1) Introduction to Mineral Identification THE SILICATE MINERALS For this assignment you will require: a streak plate, glass plate, magnet, dilute hydrochloric (HCl) acid, microscope, contact goniometer, and various mineral samples (all provided by instructor). Objectives for chapter 1: you should be able to recognize and describe the physical properties of minerals; use a mineral identification key to name minerals; identify several minerals by sight; and list the uses of several minerals that are mined. To be able to identify minerals based upon their physical properties and to be able to determine the streak, hardness, cleavage, luster and other special physical properties of these and other minerals. If you cannot see any of a mineral (no powder is produced) it has no streak. If you see a white powder, the mineral has a white streak, which is not the same as having no streak. Otherwise, describe, as specifically as possible, the color of the streak. Small variations are important! When asked about : answer metallic or nonmetallic. When asked about, answer with a number 1-10 or a small range (i.e., 4-5). Verify and write the exact hardness listed in your Manual in the space provided! REMEMBER to double check with the hardness listed in your lab manual! Use your glass plate, fingernail, MOHS SCALE OF, etc. to determine hardness. When asked about CLEAVAGE, give the number of cleavage planes and the angle(s) between them. If a sample does not have cleavage write FRACTURE in the space provided. Sometimes the cleavage surfaces are too small to see clearly, in which case cleavage may be Not Prominent. When asked about FEEL answer earthy, greasy, glassy, chalky, soapy, etc. SPECIAL PHYSICAL PROPERTIES include: reaction with acid (HCL), reaction with acid (HCL) if powdered, very high specific gravity (density), magnetism, salty taste, specific odor, ability to burn, striations on cleavage plane, and intergrowth patterns (veinlets), and double refraction. Use Table 1.2 to determine if the mineral has an economic use or if it is just a common rock forming mineral. You will need to be able to determine these physical properties and use them to identify these minerals for this laboratory assignment and for the Mineral Exam. Practice Problems: THE FOLLOWING QUESTIONS REFER TO CHAPTER 1 IN YOUR MANUAL (Use the mineral identification key, figure 1.24 (8 th edition) to identify minerals based upon their physical characteristics, start with their luster, then color or streak, hardness, cleavage, etc.) 1. Use the mineral identification key figure 1.24 (8 th edition) to determine the name of the mineral with the following properties: non-metallic luster, light-colored, softer than a fingernail, produces small thin plates or sheets when scratched by a fingernail, white color, and a soapy feel. Mineral Name: 2. Use the mineral identification key figure 1.24 (8 th edition) to determine the name of the mineral with the following properties: Non-metallic luster, very soft and can be scratched by a fingernail, white in color, with fracture and a chalky feel and earthy smell when damp. Mineral Name: Instructor: Ms. Terry J. Boroughs 1

2 Identify the physical properties for the mineral Corundum using the identification tables and table 1.1 in your laboratory manual. CORUNDUM Augite Biotite Garnet Hornblende (Amphibole) Kaolinite List of Possible Minerals (The Silicates): Muscovite Olivine Plagioclase feldspar Potassium feldspar Quartz (Color Varieties: Amethyst, Citrine, Milky, Rose, Smoky, etc.) Talc MINERAL IDENTIFICATION: THE SILICATES SAMPLE A. SAMPLE B. SAMPLE C. SPECIAL PHYSICAL PROPERTY Instructor: Ms. Terry J. Boroughs 2

3 SAMPLE D. SAMPLE E. Several varieties of this mineral are possible. Make sure you look at the different types! SAMPLE F. SAMPLE G. CLEAVAGE or CRYSTAL FACES? (pick one) Are the angles associated with the question above at 90 degrees or Not at 90 degrees? (circle one) Instructor: Ms. Terry J. Boroughs 3

4 SAMPLE H. SPECIAL PHYSICAL PROPERTY SAMPLE I. SAMPLE J. Notice the soapy or greasy feel of this sample. SAMPLE K. CLEAVAGE or CRYSTAL FACES? (pick one) Instructor: Ms. Terry J. Boroughs 4

5 The following questions are extra credit points! THE FOLLOWING QUESTIONS REFER TO THE SUMMARY / REPORT PAGE in chapter 1. (Read the questions from your manual and place your answers in the following spaces provided.) 1. Name the physical property (hardness, color, etc.) described by each of the following statements. Mineral breaks along rough, jagged, irregular surfaces: Mineral breaks along smooth planes: Mineral is scratched by a copper penny: Shines like a metal: Produces a red powder on a porcelain plate: 2. What term is used to describe the geometric shape of a mineral that has three directions of cleavage that intersect at 75 and 105 degrees? 3. Describe the cleavage of these minerals (include both the number of directions and angles between [at 90 degrees or NOT at 90 degrees]): Biotite: Galena: Hornblende: Potassium and plagioclase feldspar: 4. Identify several minerals and identify the specific hardness associated with that mineral. Mineral: Hardness: Mineral: Hardness: 5. Identify a Silicate mineral: 6. Identify a Non-Silicate mineral: The End! Instructor: Ms. Terry J. Boroughs 5