MINERAL IDENTIFICATION PRACTICE ANSWERS

Mineral Name AppearanceHardnessLusterStreak Fracture/ Cleavage Iron Pyrite  Golden  Looks like metal  Shiny  Brass yellow Above 5.5 Metallic Shiny Greenish- black to brownish- black Fracture Talc  Grayish  Has many other colors 1 to 2 Non-Metallic Waxlike or pearly White to pearl black Fracture Mica Dark brown Grayish Shiny Flat Smooth 1 Non-Metallic Shiny Reflective colorless to a very pale brown in color Cleavage

Conclusion: 1.Explain the difference between the vocabulary words in each of the following sets: A - cleavage – fracture Cleavage - The tendency of a mineral to break along flat surfaces determined by the structure of its crystals. Fracture - The tendency of a mineral to break along curved surfaces without a definite shape and break irregularly. B - appearance– luster Appearance – What does the mineral look like. Try be a descriptive as possible Luster - The quality and intensity of light reflected from the surface of a mineral. C - metallic – non-metallic Metallic – Looking like shiny metal Non-Metallic – Not looking like metal, can be dull or shiny

2. Describe how you use a Mohs scale to determine the hardness of a mineral. (Mohs scale seen on page 15). Difficulty: Easy Time Required: mere seconds Here's How: Find a clean surface on the specimen to be tested. Try to scratch this surface with the point of an object of known hardness, by pressing it firmly into and across your test specimen. For example, you could try to scratch the surface with the point on a crystal of quartz (hardness of 9), the tip of a steel file (hardness about 7), the point of a piece of glass (about 6), the edge of a penny (3), or a fingernail (2.5). If your 'point' is harder than the test specimen, you should feel it bite into the sample.known hardness Examine the sample. Is there an etched line? Use your fingernail to feel for a scratch, since sometimes a soft material will leave a mark that looks like a scratch. If the sample is scratched, then it is softer than or equal in hardness to your test material. If the unknown was not scratched, it is harder than your tester. If you are unsure of the results of the test, repeat it, using a sharp surface of the known material and a fresh surface of the unknown. Most people don't carry around examples of all ten levels of the Mohs hardness scale, but you probably have a couple of 'points' in your possession. If you can, test your specimen against other points to get a good idea of its hardness. For example, if you scatch your specimen with glass, you know its hardness is less than 6. If you can't scratch it with a penny, you know its hardness is between 3 and 6. The calcite has a Mohs hardness of 3. Quartz and a penny would scratch it, but a fingernail would not.