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