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Unformatted text preview: Geol 105 Lab 4 Week of Feb. 6-10, 2012 THE WONDERFUL WORLD OF MINERALS There are three parts to the lab this week. In PART I you will learn about some of the different properties that help us identify and understand minerals, and you will be asked to identify minerals in three rocks (one igneous, one sedimentary, and one metamorphic). In PART II you will be introduced to forensic geology and asked to solve a mystery about Darth Vader, the Berkeley hippie. And in PART III , you will be asked to identify a few common minerals. PART I. -A - PHYSICAL PROPERTIES Each station in this section has specimens that illustrate an important physical property . Visit each station, in any order, and answer the questions. The more you work with the minerals at each station, the easier it will be for you to identify the minerals in the rocks, and the minerals unknowns. LUSTER This is the appearance of light reflected from a mineral. Two basic types are contrasted at this station METALLIC and NONMETALLIC. Sort the samples into two groups: metallic vs. nonmetallic, then write down the numbers of the minerals with a METALLIC luster. #__________ AND #__________ NONMETALLIC . Match the sample number (# 13 biotite, #15 talc, #17 hematite) with the following descriptive terms: Vitreous __________ Earthy __________ Pearly __________ STREAK Streak is the color of a mineral when powdered. The streak test can be used to identify minerals with metallic luster. What is the streak of: Sample 8 (hematite) ____________________ Sample 9 (pyrite) ____________________ Sample 10 (galena) ____________________ 1 of 6 HARDNESS If a mineral scratches glass, then its hardness is greater than 5.5 on Mohs Hardness Scale- SEE PAGE 64, lab manual . If the mineral does not scratch glass, the hardness is less than 5.5. Which mineral will scratch glass? Which minerals can you scratch with your fingernail? Rank samples 22, 23, and 24 in order of relative hardness from soft to hard ________ ________ ________ CLEAVAGE AND FRACTURE Cleavage is an expression of the internal arrangement, or precise atomic stacking of crystals. Cleavage is the property of breaking along flat surfaces these surfaces are reflective and easy to see in strong light. Fracture is not the same as cleavage. Fracture is breakage in a nonplanar, random manner. The mineral quartz has conchoidal fracture, like broken glass. Which samples display more than one direction of cleavage (i.e., more than one cleavage plane)? How many cleavage planes does sample #40 have? Sample 41?...
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This note was uploaded on 04/02/2012 for the course GEOL 105 taught by Professor Platt,davis during the Spring '08 term at USC.
- Spring '08