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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
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.
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.
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.
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
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.