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