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Chapter 5 Minerals of Earth’s Crust

Chapter 5 Minerals of Earth’s Crust. Define Mineral. Give one example

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Chapter 5Minerals 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.

Four basic questions: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 Characteristics of Minerals

• More than More than 30003000 known minerals known minerals

• Fewer than Fewer than 2020 common minerals 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

Section 1 Kinds of Minerals

Rocks are Rocks are aggregatesaggregates(mixtures of minerals)(mixtures of minerals)

Chapter 5

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 1 Kinds of 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 Identifying Minerals

Five special properties that may help identify certain minerals

•Color

•Streak

•Luster

•Cleavage and Fracture

•Hardness

Section 2 Physical Properties of Minerals

Color

• While color is a property that is easily observed, it is unreliableunreliable 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 FractureCleavage 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.