Transcript Ch 5-Minerals of Earth`s Crust

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 crustQuartz, 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
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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
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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