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Margaret Gillespie September 5, 2006 Pre-Lab Worksheet for Lab #1 Physical Properties of Minerals Reading: p. 1-18 Use the following web address to answer the questions: http://mineral.galleries.com/minerals/ physical.htm 1. Why is color not always a useful mineral property? The color we see in minerals is due to the level of absorption of light wavelengths. For example, when pure white light hits a crystal, some of the wavelengths are absorbed while others are emitted. Whether the wavelengths are emitted or not is determined by atomic bonds. Bonds to different elements cause different colors to be produced. Even the slightest amount of element can strongly influence the color of a mineral. 2. What is luster? What are the four types of luster the web shows us by pictures? “Luster is a description of the way light interacts with the surface of a crystal. This is how you would tell someone how a mineral looks. It has nothing to do with color or shape, but is related to transparency , surface conditions, crystal habit and index of refraction.”
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Unformatted text preview: (http://mineral.galleries.com/minerals/property/color.htm ) The four types: Submetallic Luster, Vitreous Luster, Dull Luster and Resinous Luster 3. What are cleavage and fracture? What is the difference between them? Cleavage – result of a mineral breaking. Fracture – how the mineral breaks. How hard is a fingernail? On the Mohs Hardness Scale, 2.5 ( Gypsum ) How hard id a penny? On the Mohs Hardness Scale, 3.5 ( Calcite ) How hard is glass? On the Mohs Hardness Scale, 5.5 ( Apatite ) How hard are diamonds? ( Diamond ) 5. Is the streak of a mineral always the same as the color of it? Why? While streak is often closely linked to color, it is a different property. Streak is “the color of the powder of a mineral. It is called streak because the proper way to test for streak is to rub a mineral across a tile of white unglazed porcelain and to examine the color of the "streak" left behind.”...
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