Transcript Document
Chapter 5 Minerals of Earth’s Crust Define Mineral. Give one example. Section 1 What Is a Mineral? • Minerals are: • • • • • Naturally occurring, Usually inorganic solid, Characteristic chemical composition, Orderly internal structure, Characteristic set of physical properties. Section 1 Characteristics of Minerals Four basic questions: • 1. Is the substance inorganic? • 2. Does the substance occur naturally? • 3. Is the substance a solid in crystalline form? • 4. Does the substance have a consistent chemical composition? • See Table 1 page 103 Section 1 Kinds of Minerals • More than 3000 known minerals • Fewer than 20 common minerals Section 1 Kinds of Minerals • 10 common minerals make up 90% of the mass of the Earth’s crust. • All minerals can be classified into 2 types. – Silicates – Nonsilicates Rocks are aggregates (mixtures of minerals) Chapter 5 of Minerals Section 1 Kinds Silicate Minerals • A mineral that contains a combination of silicon and oxygen, and that may also contain one or more metals • Common silicate minerals include quartz, feldspars, micas ,and ferromagnesian minerals, such as amphiboles, pyroxenes, and olivines. Section 1 Kinds of Minerals Nonsilicate Minerals • A mineral that does not contain compounds of silicon and oxygen • Nonsilicate minerals comprise about 4% of Earth’s crust. • Examples: Dolomite, Halite, Silver, Corundum, Calcite, Gypsum, Pyrite, and Galena. • See Table 2 Page 105 • Skip Pages 106-108 Section 2 Identifying Minerals Mineralogists A person who examines, analyzes, and classifies minerals. Section 2 Identifying Minerals Physical Properties of Minerals •Many properties can be identified by just looking at a sample of the mineral. •Other properties must be identified through simple tests. Section 2 Physical Properties of Minerals Five special properties that may help identify certain minerals •Color •Streak •Luster •Cleavage and Fracture •Hardness Color • While color is a property that is easily observed, it is unreliable for the identification of minerals. • The color of a mineral sample can be affected by the inclusion of impurities or by weathering processes. Color• These are all quartz with different minerals in them. Streak- the color of a mineral in powdered form • Streak is determined by rubbing some of the mineral against an unglazed ceramic tile called a streak plate. • Much more reliable than color. • The streak may differ from the solid color of the mineral. • Minerals harder than the ceramic tile will leave no streak. Streaks Luster • A mineral is said to have a metallic luster if the mineral reflects light as a polished metal does. • All other minerals have nonmetallic luster. • There are several types of nonmetallic luster, including glassy, waxy, pearly, brilliant, and earthy. Luster- the way in which a mineral reflects light Cleavage and Fracture • Cleavage- the tendency of a mineral to split along specific planes of weakness to form smooth, flat surfaces • Fracture- the manner in which a mineral breaks along either curved or irregular surfaces Cleavage- Fracture- Hardness • Hardness is a measure of a minerals ability to resist scratching. • Hardness does not mean it will not break. • Mohs hardness scale the standard scale against which the hardness of minerals is rated. Crystal Shape Chapter 5 Density • Is the ratio of the mass of the mineral to the volume of the mineral. • Some minerals feel heavier than others.