Property Descriptions and Testing Procedures

Transcription

1 Lab 1: Mineral Identification OLLI Rock ID and Geologic Mapping Name: Introduction: In this lab activity you will become familiar with minerals and identifying their different properties. This lab will also introduce you to the deductive process where you will utilize the results of each property test to identify the name of the mineral from an established key. Materials provided: Procedure: Streak plate Penny Nail Metal plate 1. Go through and test each mineral for: Hardness Color Streak Glass Magnet Dilute HCl Hand lens Cleavage/fracture Density Luster 2. Be sure to record all information in the data table 3. After you have tested all minerals for all 6 properties, compare your results for each mineral to the established mineral chart in the back. Use this chart to identify the mineral name. Property Descriptions and Testing Procedures Color: This is probably the most easily observed property of minerals. However, color often varies widely and is the least reliable property for identification. Streak: The color of the mineral when powdered. To test for streak, draw the mineral against an unglazed porcelain tile (streak plate). Streak is more useful for identification than color. Cleavage or fracture: These two properties refer to the way in which a mineral breaks. Cleavage is an orderly breakage in well-defined planes, meaning the mineral has flat sides. Fracture is a random breakage. If a mineral breaks with rough, random surfaces, it is said to have fracture. This can vary widely so be patient and careful. Density: Compare the relative heft of a mineral by holding it in your hand and comparing it to other minerals of about the same size. In general, metallic minerals are heavier than non-metallic minerals. To simplify, we classify minerals as 1.) Light, 2.) Heavy, 3.) Very heavy. Density = mass/volume 1

2 Hardness: A mineral s hardness is it s resistance to scratching. Mohs Scale of Hardness, this scale uses common everyday objects to test hardness of each mineral sample. Below is the resulting table. Moh s Hardness Scale Rating Type Mineral Object used to test Hardness Talc Gypsum Calcite Fluorite Apatite Feldspar Quartz Topaz Corundum Diamond Talc Fingernail-2.5 Penny-3.5 Nail-4.5 Glass-5.5 Steel file-6.5 Streak plate-7 Luster: Refers to the way that a mineral reflects light. The simplest distinction is between metallic luster (shiny and gold or silver color) and nonmetallic luster (does not look like a metal in color, although it may be shiny). Particular types of nonmetallic luster include pearly, vitreous (glassy), resinous (has the appearance of resin), silky, and earthy (dull). Other properties Here are three additional tests that you should perform on all your rocks. If you get a positive test, record it in your other properties column. TASTE TEST: Certain Minerals have a particular taste. Two minerals, halide and quartz, are very similar in appearance. One simple way to tell them apart is that halide has a salty taste whereas quartz has no taste. SMELL TEST: Certain minerals give off a very distinct smell. Sulfur, for instance, smells like rotten eggs. ACID TEST: You should test your rocks to see if they will react with hydrochloric acid. Put a single drop on each rock, one at a time. If you immediately see a vigorous fizzing, it is calcite. Dolomite reacts only when scratched. MAGNET TEST: If one of your rocks is attracted to a magnet, it may be magnetite. But check all the other properties too because other iron ores are also easily magnetized. 2

3 # Mineral Name (fill in last) 1 Color Streak Hardness Cleavage or Fracture Density/Heft (Light, Medium, Heavy) Name: Luster Metallic/Non- Other Metallic Properties/Notes

4 Mineral Name Possible Colors Streak Hardness Cleavage or Fracture Density/Heft Light, Medium, Heavy Luster Metallic/Non- Metallic Azurite Blue Blue Cleavage Light Non-Metallic Other Properties/notes Biotite Brown None Cleaves 1 plane Light Non-Metallic, glassy, almost translucent Calcite Clear to milky, orange, tan White 3 Cleavage Light Non-Metallic, vitreous-pearly Very flexible Reacts with acid Chalcopyrite Feldspar Galena Brassy, Yellow, reddish Gray, green orange Blue black, grey Greenish-black Fractures Heavy Metallic Colorless 6 Two planes of cleavage that meet at right angles Light Non-Metallic Grey-black 2.5 Cleavage Heavy Metallic Crystals maybe cut, very heavy Garnet Red, orange, purple, green Colorless 7 Fracture Medium Non-Metallic, vitreous Octahedral crystals Graphite Grey Grey 1.2 Cleavage Light Metallic Draws on paper Gypsum Pinkish-white, white, grey, reddish-brown White scratches with fingernail Cleaves Light Non-Metallic, vitreous-silky

5 Mineral Name Possible Colors Streak Hardness Cleavage (how many planes) or Fracture Halite Clear, white None 2.5 Cleaves at right angles Density/Heft Light, Medium, Heavy Luster Metallic/Non- Metallic Other Properties Light Non-Metallic Tastes salty Hematite Black, grey, reddish-brown Reddish-brown Fracture Heavy Metallic or rusty Hornblende Dark green, shiny bluishblack Gray to white 5-6 Cleaves into needlelike fragments Magnetite Grey-black Black 6 Non cleavage, but octahedral parting Muscovite Clear, white, light brown Colorless, light brown Cleaves in 1 plane Light Non-Metallic, vitreous crystals are needle shaped Heavy Metallic Magnetic Light Non-Metallic, vitreous-pearly Flat flexible crystals Pyrite Golden-brassy, yellow Greenish black Fracture Medium Metallic Quartz Clear, white, purple, rose, grey None 7 No cleavage, but conchoidal fracture Light Non-Metallic, vitreous Sulfur Yellow White Fractures Light Non-Metallic, resinous-dull Talc White, green White 1 Cleaves Light Non-metallic, Greasy/pearly Smells like eggs Powdery-greasy feel

6 Lab 1: Mineral identification OPTIONAL worksheet OLLI Rock ID and Geologic Mapping Name: This is a review to keep you fresh on the material. It can be filled out after class/lab. 1. What are the 6 properties used to identify minerals a. b. c. d. e. f. 2. Briefly describe how you would test a mineral for each of these properties a. b. c. d. e. f. 3. What tool is used to determine the streak of a mineral? Answer: 4. What is the name of the scale used to determine hardness? Answer: 5. What is the difference between cleavage and fracture? 6. What are the two major categories of luster? Answer: 7. List types of Non-Metallic Luster Answer: