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Ch 5-Minerals of Earth’s Crust. Objectives Compare main groups of minerals Identify the types of silicate crystalline structures Describe common nonsilicate crystalline structures Describe physical properties that help distinguish minerals from one another
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Ch 5-Minerals of Earth’s Crust • Objectives • Compare main groups of minerals • Identify the types of silicate crystalline structures • Describe common nonsilicate crystalline structures • Describe physical properties that help distinguish minerals from one another • List special properties that help identify certain minerals
Characteristics of Minerals • Define mineral • Natural, usually inorganic solid, has special chemical composition, orderly internal structure, characteristic set of physical properties
Main groups of Minerals • 4,000 kinds of minerals • Fewer than 20 are common • Forming minerals=common minerals that form the rocks that make up Earth’s crust • 10 minerals that make up 90% of Earth’s crust-Quartz, orthoclase, plagioclase, muscovite, biotite, calcite, dolomite, halite, gypsum, ferromagnesian • 2 groups-silicate and nonsilicate minerals • Based on chemical composition
Silicate Minerals • Mineral that contains combination of silicon and oxygen • Feldspars are most common • Make up 96% of Earth’s crust • Feldspar and quartz make up 50%
Nonsilicate Minerals • Minerals that do not contain compounds of silicon and oxygen • 4% of Earth’s crust • Carbonates, halides, native elements, oxides, sulfates, sulfides
Silicate Crystalline Structures • Minerals in Earth’s crust all have crystalline structure • Crystal-solid whose atoms, ions, or molecules are arranged in regular repeating pattern • Types of crystalline structures • Isolated tetrahedral silicates • Ring silicates • Single chain silicates • Double chain silicates • Sheet silicates • Framework silicates
Nonsilicate Crystalline Structures • Variety of crystalline structures • Cubes, hexagonal, prisms, irregular masses • Similar to silicates but center is not silicon • If mineral has same ion at center of tetrahedral, commonly share similar crystal structures
Sec 2-Identifying minerals • Physical properties of minerals • Color • Streak-color of powder • Luster-light reflected from mineral’s surface • Cleavage-ability to split • Fracture-ability to fracture • Hardness-ability to resist scratching • Mohs Hardness Scale • Crystal shape • Density-ratio of mass to volume • Mineralogists-Earth scientists that examine, analyze, and classify minerals. Use the physical properties
Other properties of minerals • Fluorescence & phosphorescence • Ability to glow under ultraviolet light, and after light is turned off • Chatoyancy and Asterism • Reflected light minerals display silky appearance. Six sided shape appears when mineral reflects light • Double refraction • Crystals bend light, produce double image of any object viewed through them
Magnetism • Minerals that contain iron • Ex. Magnetite • Radioactivity • Arrangement of protons and neutrons in nuclei of some atoms is unstable • Ex. Uranium and radium